Navigated Surgical System Including Override Option

ABSTRACT

A surgical system including a surgical tool and a navigation system for tracking the position of the surgical tool. The surgical tool comprising a housing including a variable speed motor and control module disposed within the housing. The navigation system comprising a navigation console in communication with the control module of the surgical tool, the navigation console may be configured to communicate instructions to the control module of the surgical tool based on the position of the surgical tool relative to a defined zone. The navigation console may be configured to deactivate the surgical tool based on the position of the surgical tool relative to the defined zone. The navigation console may also be configured to provide a user-selectable override option to allow continued operation of the surgical tool within the defined zone.

RELATIONSHIP TO EARLIER FILED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/978,364 filed May 14, 2018, now U.S. Pat. No. ______. ApplicationSer. No. 15/978,364 is a continuation application of U.S. patentapplication Ser. No. 15/405,462 filed Jan. 13, 2017, now U.S. Pat. No.10,004,517. Application Ser. No. 15/405,462 is a divisional of U.S.patent application Ser. No. 14/169,437 filed 31 Jan. 2014, now U.S. Pat.No. 9,559,624. Application Ser. No. 14/169,437 is a divisional of U.S.patent application Ser. No. 12/617,052 filed 12 Nov. 2009, now U.S. Pat.No. 8,657,482. Application Ser. No. 12/617,052 is a divisionalapplication based on from U.S. patent application Ser. No. 11/472,012filed 21 Jun. 2006, now U.S. Pat. No. 7,638,958. Application Ser. No.11/472,012 claims priority under 35 U.S.C. Sec. 119 from U.S.Provisional Pat. App. No. 60/694,592 filed 28 Jun. 2005 and U.S.Provisional Pat. App. No. 60/809,645 filed 31 May 2006. The contents ofthe applications from which the present claims priority are explicitlyincorporated herein by reference.

FIELD OF THE INVENTION

This invention is generally related to electrically powered surgicaltools. More particularly, this invention is related to a cordless,powered surgical tool with a sealed module in which the circuit thatcontrols the activation of the tool is enclosed.

BACKGROUND OF THE INVENTION

In modern surgery, one of the most important instruments available tomedical personnel is the powered surgical tool. Often this tool is inthe form of a drill unit in which a motor is housed. Secured to thedrill unit is a cutting attachment designed for application to asurgical site on to perform a specific medical procedure. For example,some powered surgical tools are provided with drills, burs or reamersfor cutting bores into tissue or for selectively removing tissue such asbone. Other powered surgical tools are provided with saw heads. Thesetools separate large sections of hard and soft tissue. A wire driver isa power tool that, as its name implies, drives a wire into a patient,more particularly, a bone. Power tools are also used to perform otherfunctions in the operating room. For example, it is known to use a powertool to mix the components that form a mass of surgical cement.

The ability to use powered surgical tools on a patient lessens thephysical strain of surgeons when performing medical procedures on apatient. Moreover, most surgical procedures can be performed morequickly and more accurately with powered surgical tools than with themanual equivalents that preceded them.

One type of powered surgical tool that is especially popular with somephysicians is the cordless, battery-operated powered surgical tool. Asthe name implies, this tool has a battery that serves as the powersource for the motor. This eliminates the need to provide the tool witha power cord connected to an external-power source. Elimination of thepower cord offers benefits over corded, powered surgical tools. Surgicalpersonnel using this type of tool do not have to concern themselves witheither sterilizing a cord so the cord can be introduced into the sterilesurgical field or ensuring that, during a procedure, an unsterilizedsection cord is not inadvertently introduced into the surgical field.Elimination of the cord also results in the like elimination of thephysical clutter and field-of-view blockage a cord brings to a surgicalprocedure.

One feature shared by both corded and cordless power surgical tools isthe presence of a control switch or member on the tool. This member isoften in the form of a biased switch, trigger or button. A number ofcorded and cordless surgical tools have handles similar to pistolhandgrips. A tool of this shape is sometimes designed so the controlmember is trigger that is slidably mounted to the handle.

Powered surgical tools, unlike many other power tools, have to do morethan deliver relatively large amounts of power. A powered surgical toolmust be able to withstand repeated exposure to an environment bothsaturated with water vapor and very hot. This is because, prior to use,a powered surgical tool is autoclave sterilized. In this process, thetool is placed in a chamber where there is atmosphere is saturated withwater vapor (steam), the temperature is approximately 270° F. and theatmospheric pressure is approximately 30 psi (Gage). Internal componentsof the tool, including the conductive components of its control circuit,if left unprotected in and repeatedly exposed to this environment,corrode.

The Applicant's U.S. Pat. No. 5,747,953, CORDLESS, BATTERY OPERATEDSURGICAL TOOL, issued May 5, 1998, and incorporated herein by reference,discloses one means for protecting the internal components of a surgicaltool from the effects of autoclave sterilization. The tool of thisinvention has a sealed module that houses the circuit that regulatestool actuation. Also internal to this module are contactless sensorsthat monitor the states of externally mounted triggers. Attached to eachtrigger and located inside the tool housing is a magnet. Internal to themodule are magnetic field sensors. Each sensor generates a varyingsignal as a function of the proximity of an associated one of thetrigger magnets. The manual displacement of the trigger results in alike displacement, inside the tool, of the magnet. When a trigger andmagnet are so displaced, the complementary sensor generates a signalthat indicates the movement has occurred. Upon receipt of this signal,the control circuit generates the signal needed to allow an energizationcurrent to be applied to the motor.

The electrically conductive components of the on/off control assembly ofthe above tool are shielded from the supersaturated heated air of theautoclave environment. When this tool is sterilized, these componentsare not adversely affected.

However, known cordless power tools have other sensitive components thatremain exposed. These components typically include the sensors thatmonitor the operation of the power-producing units. Many motorizedcordless power surgical tools, for example, employ brushless DC-motorsas their power-producing units. Internal to this type of motor aresensors that monitor the position of the motor's rotor. The signalsproduced by the sensors are supplied to the control circuit. Thesesignals function as feedback signals that, with the on/off signals,regulate the commutation of the motor.

These sensors are exposed to the corrosion fostering environment of theautoclave. Currently, these sensors are encased in a potting compound toshield them from the harsh effects of the sterilization process.Nevertheless, over time, pressurized water vapor can reach thesesensors. Once this occurs, the water vapor has a tendency to corrode thesensors so as to cause their malfunction.

Even when these sensors remain shielded from the saturated water vapor,there are some disadvantages associated with their use. Often, thesesensors operate best in low temperature environments. For example, thesignals generated by Hall effect sensors start to vary at temperaturesabove 150° C. The motor integral with a powered surgical tool cangenerate enough heat to cause the temperature to rise above this level.Once this occurs, the variations in the signals output by the Hallsensors can cause the control circuit to generate control signals thatfoster tool malfunction.

Moreover, the accuracy of the motor rotor position signals generated bythese sensors is naturally very dependent on sensor position relative tothe rotor. Despite the best efforts of surgical personnel, it is notunheard of for surgical tools to drop to the floor. When a tool isexposed to this type of mechanical shock, the positions of the motorrotor sensors can shift. Such movement is still another reason why thesensors may to generate signals that do not accurately represent motorrotor position.

In theory, it should be possible to eliminate this problem by using theback EMF signals generated by the motor windings to obtain an indicationof rotor position. This is how use of rotor position sensors in cordedpowered surgical tools is eliminated. In practice, it has provendifficult to implement this solution in a cordless powered tool. This isbecause, at zero speed, stall speed, there are no back EMF signals fromwhich rotor position can be determined. Instead, other means areemployed to energize the motor windings in order to start up the motor.These other means typically involve the application of significantcurrents to the windings. During a surgical procedure, a cordless powertool may be repeatedly cycled on and off. Therefore, if a cordlesspowered surgical tool were driven based on the state of back EMFsignals, the power required to constantly restart the motor can resultin relatively rapid depletion of the battery charge. This could requirethe battery to be changed in the middle of the procedure. Clearly, thisis a task surgical personnel would like to avoid.

Moreover, many powered surgical tools, both of the corded and cordlessvariety, drive different cutting accessories. For example, many drillunits are designed to drive both shavers and burs. Often, differentaccessories operate at different preferred speeds have different maximumoperating speeds. A number of different assemblies are commerciallyavailable that provide feedback to the control console that energizes acorded power tool to indicate the type of attached cutting accessory.Based on this information, the control console regulates actuation ofthe tool so it operates at speeds appropriate to the attached accessory.However, a cordless power tool does not have a control console. Thus, ithas proven difficult to provide a mechanism that can be used to customregulate the operation of the tool based on the attached accessory.

Moreover, some corded powered surgical tools have control consoles ableto provide custom speed or operation settings based on surgeonpreference. Again, since a cordless tool is not connected to this typeof console, it has proven difficult to provide surgeons with this typeof control with this type of tool.

SUMMARY OF THE INVENTION

This invention is related to a new and useful powered surgical tool. Thesurgical tool of this invention does not rely on sensors integral withthe tool power producing unit to determine the operating state of theunit. The surgical tool of this invention is also custom configurablebased on the type of attached cutting accessory and/or surgeonpreferences.

The powered surgical tool of this invention includes a handpiece thatcontains the power-producing component. Often this component is a DCmotor. Also internal to the handpiece is a module that contains thecontrol circuit that regulates the application of power to the motor.This control circuit is contained in a sealed module. Also internal tothis housing are sensors that monitor the state of the actuation membersattached to the handpiece and sensors that monitor the position of themotor rotor.

Since the handpiece of this invention does not have sensors integralwith the motor, the problems associated with providing these sensors iseliminated.

The handpiece of this invention also has a processor that monitors thestate of the signals generated by the actuation of the control members.The processor executes a specific set of operating instructions loadedeach time the tool is set up for use in a procedure. Based on theseinstructions, the processor is directed to execute the received signalsrepresentative of control member actuation, the processor generates aspecific set of control instructions.

The instructions selected for processor execution are loaded from acomponent remote to the tool. If the particular tool is a cordless tool,the instructions are transmitted by a wireless communications link.Thus, the powered surgical tool of this invention is custom configuredfor operation based on variables such as type of attached cuttingaccessory and surgeon preference.

In one embodiment, the powered surgical tool of this invention is acordless tool. In other embodiments of this invention, the tool iscorded.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the claims. The aboveand further features of this invention may be better understood byreference to the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a side view of a powered tool incorporating the features ofthis invention;

FIG. 1A is a cross sectional view of a powered tool of this invention;

FIG. 2A is an exploded view of a trigger assembly the tool of thisinvention;

FIG. 2B is a cross sectional view of the trigger assembly;

FIG. 3A is cross sectional view of the control module;

FIG. 3B is an exploded view of the panel members that form the controlmodule;

FIG. 3C is a plan view of the interior of the control module;

FIG. 3D is a perspective view of the interior of the control moduleillustrating some of the components mounted to and in the module;

FIG. 4A is a side and partial cross-sectional view illustrating thearrangement of a trigger switch magnet to the sensors internal to thecontrol module that monitor the position of the trigger switch;

FIG. 4B is a side and partial cross sectional view of how the sensorsthat monitor motor rotor position are mounted to the printed circuitboard internal to the control module;

FIG. 5 is a cross-sectional view illustrating how the power FETs aremounted to the control module;

FIG. 6 is an assembly diagram illustrating how FIGS. 6A, 6B, 6C, 6D and6E are assembled to from a schematic and block diagram of the controlcircuit of this invention;

FIG. 7 is a block diagram of the main sub-circuits that form the motorcontrol circuit;

FIGS. 8A, 8B, 8C and 8D collectively form a flow chart of the processsteps executed by the components internal to the tool upon actuation ofthe tool;

FIG. 9 are plots of the signals generated by the control module sensorsthat monitor the position of the motor rotor of the tool;

FIG. 10 is a plot of the waveform of the output signal generated by theprimary sensor that monitors motor rotor position;

FIGS. 11A-11D collectively form a flow chart of the process stepsexecuted by a processor integral with the tool control module in orderto generate digital signals representative of motor rotor position asthe rotor turns;

FIG. 12 depicts some of the data stored in a permanent memory integralwith the control module processor;

FIG. 13 depicts some of the data stored in a random access memoryintegral with the control module processor;

FIG. 14 is a plot of an alternative waveform of the output signalgenerated by the primary sensor that monitors motor rotor position;

FIG. 15 is a flow chart of the process steps executed to update thesignal transition levels against which the motor sensor output signal iscompared;

FIG. 16 is a block diagram of the components internal to the tool ofthis invention that facilitate the variable configuration and remotecontrol of the tool;

FIG. 17 is a system diagram illustrating the components external to thetool that used to externally configure and control the tool;

FIG. 18 is a diagrammatic view of a how a tool of this inventionexchanges data and instructions with a handpiece control console througha corded power pack;

FIG. 19 is a flow chart of the steps performed by the integrated toolsystem of this invention in which the tool is configured to preferencesof the surgeon;

FIGS. 20A and 20B collectively form a flow chart of the steps performedby the tool system when the tool is configured based on thecharacteristics of the attached accessory and as operated based on thesecharacteristics;

FIG. 21 is a flow chart of the process steps performed by the integratedtool system of this invention to warn and conserve operation of the toolwhen a tool component enters an exceptional operating state;

FIG. 22 is a flow chart of the process steps performed by the integratedtool to inhibit application of the tool attachment beyond application atthe surgical site at which the procedure is being performed;

FIG. 23 depicts how the integrated system of this invention is used tofacilitate the positioning of a kinematic machine such as theillustrated jig;

FIGS. 24A and 24B collectively form a flow chart of the process stepsexecuted by the system to position a surgical implant or other surgicaldevice;

FIG. 25 is a perspective view of how a surgical tool of this inventionis used to mix orthopedic cement for a predetermined amount of time andmonitor the viscosity of the cement;

FIGS. 26A, 26B and 26C collectively form a flow chart of the processsteps executed by the surgical tool system of this invention to ensurethe cement is mixed for an appropriate amount of time and to monitor theviscosity of the cement;

FIG. 27 is a perspective view of how data regarding the characteristicsof the components forming the cement to be mixed are supplied to thesystem;

FIG. 28 depicts some of the data types stored in the data storage deviceintegral with the packet containing surgical cement;

FIG. 29 depicts some of the data types stored in the data storage deviceintegral with the container storing the monomer used to cure thesurgical cement;

FIG. 30 depicts some the data types stored in the data storage deviceintegral with a surgical implant;

FIG. 31 is a plot of the change of current drawn over time when thesystem of this invention is employed to mix surgical cement;

FIG. 32 is a side view of an alternative tool housing of the surgicaltool of this invention;

FIG. 33 is a plan view of the bottom surface of the proximal end of thehousing head when viewed from line 33-33 of FIG. 32;

FIG. 34 is a partial schematic view of the electrical componentsinternal to the alternative tool showing how signals are exchanged withbetween the tool control processor and the auxiliary unit and how thepower from the battery connected to the tool is selectively supplied tothe auxiliary unit;

FIG. 35 is a diagrammatic illustration of how a flux pipe serves as theconduit for conducting the energy emitted by the tool power generatingunit to the sensor in a remotely located control module;

FIG. 36 is a graphic depiction of how the tool control processor can beprogrammed to vary the USER_SPEED signal non-linearly as a function ofthe displacement of the tool actuating member;

FIG. 37 is a wave form of the signal generated by a sensor monitoringthe state of a two pole rotor wherein the plot points are used toillustrate the measurements taken during execution off the baseassumption algorithm; and

FIG. 38 is a flow chart of the steps executed as part of the baseassumption algorithm of the tool of this invention to determine rotorposition at start up with a single sensor.

DETAILED DESCRIPTION I. Surgical Power Tool

A. Overview

FIGS. 1 and 1A illustrate a power tool 30, a surgical tool, constructedin accordance with this invention. Tool 30 has a housing 32 in which inelectrically-actuated power-generating unit is located. In the specifictool 30, this power-generating unit is a brushless, Halless, DC motor34. Tool housing 32 is shaped to have a generally cylindrical head 36 inwhich motor 34 is fitted. Extending downwardly from head 36, toolhousing 32 is shaped to have a handle 38.

Also contained in the head 36 is a coupling assembly 39 represented by aring moveably mounted to the front of housing 32. Coupling assembly 39consists of the mechanical linkage that releasably attaches a surgicalattachment 41 (FIG. 16) to the motor 34 so that the motor can actuatethe attachment. In some tool systems of this invention, attachment 41 isreferred to as a cutting accessory. The exact structure of the couplingassembly 39 is not relevant to the structure of this invention. If, asin the tool of FIGS. 1 and 1A, the power generating unit is motor 34,coupling assembly 39 consists of a locking arrangement that releasablyholds the accessory to the motor shaft 27 so that accessory rotates withthe rotation of the motor shaft. In some versions of the invention, aspeed reduction gear assembly 28 is located between motor 34 andcoupling assembly 39.

Disposed inside a void space 29 internal to the handle is a hermeticallysealed control module 40 shown in phantom in FIG. 1. Control module 40,as discussed below, contains the components that regulate theapplication of energization current to the motor 34.

Power for energizing the motor 34 is from a battery 42, shownschematically in FIG. 6E. In practice, the battery 42 is removablyattached to the butt end of the handle 38. One battery 42 that can beemployed with this version of the invention is described in theApplicant's Assignee's U.S. Pat. No. 5,977,746, entitled RECHARGEABLEBATTERY PACK AND METHOD FOR MANUFACTURING SAME issued 2 Nov. 1999 andincorporated herein by reference.

Two trigger switches 46 and 47 arranged in tandem extend forward fromthe front face of the handle 38. Each trigger switch 46 and 47 isslidably mounted to the tool housing 32. Each trigger switch 46 and 47includes a generally cylindrical barrel 50. The barrel 50 is the portionof the trigger switch 46 or 47 that extends forward of the housinghandle 38. A head 52, shaped as a fingerhold, is disposed over thedistal free end of the barrel 50. (“Distal”, it shall be understoodmeans toward the surgical site to which the tool 30 is directed.“Proximal”, means away from the surgical site.) Trigger switches 46 and47 are mounted to tool housing 32 so that the barrels 50 are located infront and are aligned with the control module 40.

B. Mechanical Features

FIGS. 2A and 2B collectively illustrate how trigger switches 46 and 47are mounted in a trigger switch housing 33. Trigger switch housing 33 isformed of plastic. The housing 33 is shaped to define two barrel cages,each of which is closed at its proximal end. Each barrel cage 35 isdimensioned to facilitate the slidable slip fitting of one of theassociated trigger switch barrels 50. A mounting plate 37 is formedintegrally with and extends around the open distal end of the barrelcages 35. Mounting plate 37 is dimensioned to fit in a recessed spacedefined by the front face of the handle 38 (recessed space notillustrated). A fitting boss 43 extends proximally rearward frommounting plate 37 between the barrel cages 35. Fitting boss 43 has anaxially extending through bore 61. A fastening member, not illustrated,extends through boss 43 to hold trigger switch housing 33 to toolhousing 32. Trigger switch housing 33 is formed with stop walls 45 thatextend across the proximal ends of barrel cages 35. Stop walls 45 arethe trigger housing structural members against which the proximal endsof barrels 50 abut when the trigger switches 46 and 47 are fullydepressed.

Helical springs 48 normally hold trigger switches 46 and 47 in the fullyextended position. Each spring 48 is seated in a longitudinal closed-endbore 49 that extends distally from the proximal end of the associatedtrigger switch barrel 50. The proximal end of spring 48 bears againsthousing stop wall 45. The spring 48 is seated around a post 51 thatextends distally forward from the inner wall of housing stop wall 45.Post 51 extends partially into barrel bore 49. Forward, distal movementof each trigger switch 46 and 47 is limited by a separate pin 53. Eachpin 53 is seated in an opening formed in the associated housing barrelcage 35 (opening not identified) and extends laterally into the spacewithin the barrel cage. The pin 53 seats in a groove 55 that extendslongitudinally along the outside of trigger barrel 50. (In FIG. 2A onlythe groove 55 of trigger switch 47 is shown.) Each groove 55 is closedat both ends so that the abutment of pin 53 against the end walls thatdefine the groove limit both forward and reverse movement of triggerswitch 46 or 47.

An O-ring 57 and a Teflon ring 59 are seated in a groove 60 that extendscircumferentially around the trigger switch barrel. Groove 60 is locatedbetween switch head 52 and longitudinal groove 55. O-ring 57 is seatedin the base of the groove 60. Teflon ring 59 is a split ring seated ingroove 60 over O-ring 57. The outer surface of Teflon ring 59 pressesagainst the inner wall of barrel cage 35. Teflon ring 59 thus provides alow friction smooth interface between the trigger switch barrel 50 andthe adjacent inner surface of the barrel cage 35.

In FIGS. 2A and 2B, a rectangular trigger assembly tool 27 is alsoshown. After trigger switches 46 and 47 are fitted into their barrelcages 45, tool 27 is slid into the barrel cages and the fitting boss 43.The opposed top and bottom ends of tool 27 seat in grooves 29 formed inthe trigger switch barrels 50. Trigger assembly tool 27 holds thetrigger switches 46 and 47 in position until pins 53 are seated in thebarrel cages and switch barrel grooves 55.

Magnets 56 and 58 are attached to each trigger switch 46 and 47,respectively. Each magnet 56 and 58 is mounted to the proximal end ofthe trigger switch barrel 50. Each trigger switch barrel 50 has a boss63 that extends proximally rearward from the proximal end of the barrel.The associated magnet 56 or 58 is seated in a closed end bore formed inthe boss 63 (bore not identified).

Each housing barrel cage stop wall 45 is formed to have a proximal endopening 65. The trigger switch barrels 50 are seated in the barrel cage35 so that when the associated switch is fully depressed, boss 60 andmagnet 56 or 58 extend proximally rearward, through the associatedopening 65, beyond the cage stop wall 45.

The depression of each trigger switch 46 or 47 thus causes theassociated magnet 56 or 58, respectively, to move closer to the controlmodule 40. Owing to the extension of the magnet 56 or 58 proximallybeyond the barrel cage 35, the magnet, relative to the body of thetrigger switch barrel 50, moves close to the control module 40. Forreasons apparent below, tool 30 of this invention is assembled so thatneither trigger switch 46 or 47 nor its complementary magnet 56 or 58contact the control module 40.

As seen in FIG. 3A, internal to the control module 40 is a printedcircuit board 64. Mounted to the printed circuit board 64 are threepairs of sensors, sensor pair 66 and 68, sensor pair 70 and 72 andsensor pair 74 and 76 (FIG. 6A). Sensor pair 66 and 68 generates signalsas a function of the relative position of magnet 56. Sensor pair 70 and72 generates signals as a function of the relative position of themagnet 58. Sensor pair 74 and 76 generates signals as a function of theoperation of the power-producing unit. In the present version of theinvention, sensor pair 74 and 76 generate signals based on therotational orientation of the motor rotor 78 shown symbolically in FIG.6D.

Also internal to control module 40 are power FETs 82 a-82 c and 84 a-84c (FIG. 6D). Each FET 82 a, 82 b and 82 c selectively ties one of themotor windings 86 a, 86 b and 86 c, (FIG. 6D) respectively, to thepositive terminal of battery 42. Each FET 84 a, 84 b and 84 cselectively ties one of the motor windings 86 a, 86 b and 86 c toground.

Mounted to printed circuit board 64 are other components discussedbelow. These components, based on the signals generated by sensor pairs66-68, 70-72 and 74-76, selectively gate FETs 82 a-82 c and 84 a-84 c.The gating of FETs 82 a-82 c and 84 a-84 c causes current flow throughthe windings 86 a-86 c to energize motor 34.

Control module 40, as seen in FIGS. 3A and 3B, is formed from sixplates. When the control module 40 is seated in the housing 32, a frontplate 92 is the most distal of the plates and extends longitudinallyinside the handle 38. Top and bottom plates 94 and 96, respectively,extend perpendicularly rearward through the handle 38 from the opposedtop and bottom edges of the front plate 92. Back plate 98 is the mostproximal of the plates. The back plate 98 extends between the proximalends of the top and bottom plates 94 and 98, respectively. Front, top,bottom and back plates 92, 94, 96 and 98, respectively, are weldedtogether to form a rectangular shell, (not identified). This shelldefines the space within module 40 in which printed circuit board 64 isseated.

Lids 102 and 104 are the remaining two plates that form module 40. Lids102 and 104 are rectangularly shaped and are seal over the opposed facesof printed circuit board 64.

Generally, the front plate 92, the bottom plate 96, the back plate 98and the lids 102 and 104 are formed of magnetic material that isnon-corrosive. One suitable material from which these components can beformed from nickel such as Nickel 200. These plates need to be magneticbecause, in the described version of the invention, sensors 66-76 aremagnetically sensitive. Forming the plates from a magnetic materialshields the sensors from ambient magnetic fields. In one version of theinvention, plates 92-98 are approximately 0.050 inches thick; lids 102and 104 are approximately 0.015 inches thick. The reduced thickness ofthe lids 102 and 104 facilitates the welding of the lids to the plates92-98.

While front plate 92 is generally formed of magnetic material, thesections of the plate that extend over the sensor pair 66 and 68 andsensor pair 70 and 72 are in the form of non-corrosive non-magneticrings 106, seen in FIG. 4A. In one version of the invention, rings 106are formed from copper or a copper-nickel alloy. One such alloy is soldunder the trademark Monel by Inco Alloys of Huntington, W. Va., UnitedStates. This alloy has a composition by weight of copper 30-35%, nickel60-65%, remainder sulfur and carbon. Each ring 106 is mounted in anindividual circular opening 107 formed in the front plate 92.

At the center of each ring 106 there is a solid disk 108 formed frommagnetic material that is non-corrosive. Materials from which it may bepossible to form disk 108 include nickel and nickel iron alloys. Onesuch alloy from which disk 108 can be formed is sold under the trademarkCARPENTER HIGH PERMEABILITY “49” by the Carpenter Steel Company ofReading, Pa., United States. This alloy has a compensation by weight ofnickel 48%, carbon 0.02%, silicon 0.35%, manganese 0.50%, balance iron.

The reason front plate 92 is formed from the different materials isunderstood by reference to FIG. 4A. Each ring 106 and disk 108 pair iscentered along the axial line of travel of one of the trigger switchmagnets 56 or 58, magnet 56 shown. This line is also the axis alongwhich the associated pair of sensors 66 and 68 or 70 and 72 is mostsensitive to changes in magnetic field. Owing to themagnetic/non-magnetic/magnetic relationship between the front plate 92,ring 106 and disk 108, these components focus the flux of the magneticfield emitted by the magnet along this line. In FIG. 4A, the magneticflux is illustrated by dashed lines 110. Consequently, slight changes influx density caused by movement of the trigger switch 46 or 47 to whichthe magnet 56 or 58 is attached are readily sensed by the sensor pair 66and 68 or 70 and 72.

Top plate 94, or at least portion thereof that covers sensors 74 and 76,is formed from a non-corrosive non-magnetic material. Copper or Monelalloy may be suitable materials from which this plate or plate sectionis formed. Top plate 94, or at least the section covering sensor pair 74and 76, is formed from non-magnetic material because sensors 74 and 76monitor changes in rotor orientation by monitoring the changes in themagnetic fields emitted by the rotor 78.

In some versions of the invention, opposed magnetic plates, notillustrated, extend upwardly from each of the lids 102 and 104. Theseplates are located on opposed sides of the location inside the controlmodule 40 where sensor 74 and 76 are mounted. These plates shieldsensors 74 and 76 from ambient magnetic fields.

Returning to FIGS. 3A, 3B, 3C and 3D, it is seen that back plate 98 isformed with a rectangular opening 108. Opening 108 functions as theopening in which a terminal board (not illustrated) is seated. Exposedcontacts integral with the terminal board are the terminal points towhich conductors (not illustrated) from a remote device are connected.The remote device serves as the head through which instructions foroperating the surgical tool 30 are supplied to the control module 40 ordata regarding the operating state of the tool are output from themodule. This remote device may be a second terminal board positionedimmediately behind an immediately removable plate over an opening in thetool housing 32 (terminal board, housing opening and plate notillustrated.) Alternatively, this remote device is the data transceiverhead 530 described with respect to FIG. 16.

Module bottom plate 96 is formed with five circular openings 111. Eachopening 111 houses a single driver/signal pin assembly 112, best seen inFIG. 5. Each driver/signal pin assembly 112 includes a copper core pin113 that extends through module plate 96. Pin 113 extends through thecenter opening of a circular, bushing 114 seated around the perimeter ofthe opening 111. Bushing 114 is formed from cold rolled steel. Acircular glass seal 115 holds the pin 113 in the center opening of thebushing 114.

A long clip connector 116 is fitted over the exposed end of each pin113. Long clip connectors 116 are the module components to which wiresto the battery 42 and windings 86 a-86 c are connected. In some versionsof the invention, one or more of the long clip connectors 116 areeliminated.

Five driver/signal pin assemblies 112 are mounted to control module 40.Two of pin assemblies 112 serve as the conductive paths wherein thepositive and negative connections to the battery 42 are made. Theremaining three pin assemblies 112 function as the conductive paths overwhich separate connections are made to the motor windings 86 a, 86 b and86 c.

A rectangular mounting plate 119, best seen in FIGS. 3B and 3C, extendslaterally forward from back plate 98 to and through front plate 92 atthe bottom of control module 40. Mounting plate 119 is formed ofmaterial that has good thermal conductive properties for reasons thatare apparent below. One such material is Nickel 200. The proximal end ofthe mounting plate 119 is seated in a rectangular slot 120 formed in thebottom plate 98 below opening 108. The distal end of mounting plate 119extends through and forward of a similar rectangular slot formed infront plate 92, (slot not identified). Mounting plate 119 is dimensionedto have a distal end section 121 located distally forward of front plate92.

When control module 40 of this invention, FETs 82 a-82 c and 84 a-84 care disposed over opposed faces of mounting plate 119. The bottom end ofcircuit board 64 is disposed over and secured to an adjacent facesurface of the top of the plate 119. When the control module 40 isfitted in handle 38, the plate distal end section 121 abuts an adjacentinner wall of the tool housing 32 that defines the space in which themodule is seated. Since plate 119 serves as both the mounting surfacefor FETs 82 a-82 c and 84 a-84 c and physically contacts tool housing 32the plate serves as a combined mounted surface and heat sink for theFETs. Distal end section 121 of mounting plate 119 further functions asa spacer to prevent the front end of control module 40 from pressingagainst the inner wall of the tool housing 32.

Mounting plate 119 also serves as a support member for circuit board 64.During assembly of control module 40, the leads to the low side FETs 84a-84 c are typically wire bonded (ultrasonically) to the printed circuitboard 64. During this operation, the mounting plate 119 functions as thebacking member that prevents the printed circuit board 64 fromvibrating.

A generally cylindrical insert 122 extends laterally inward from the topof front plate 92. Insert 122 is seated in a bore formed in the frontplate 92 (bore not identified). The insert 122 is formed with a closedend threaded bore 123, (shown in phantom) that extends inwardly from theexposed face of the insert. When control module 40 is seated in toolhousing 32, a fastener (not illustrated) fitted in bore 123 holds themodule in position.

As seen by FIG. 3C, insert 122, like the distal end section 121 ofmounting plate 119, projects a slight distance distally forward of frontplate 92. Thus, insert 122, like mounting plate 119, functions as aspacer to prevent module front plate 92 from abutting the adjacent innerwall of the tool housing 32.

Insert 122 is further formed so to have a planar surface 124. Surface124 is coplanar with the longitudinal axis of the control module 40. Apost 125 integral with the insert 122 projects away from surface 124.When the control module 40 is assembled, printed circuit board 64 isdisposed over insert surface 124. Insert 122 thus serves as a mountingbracket for holding the printed circuit board 64 in the control module40. Post 125 extends through an opening in the circuit board 64 (openingnot identified). A locking pin retainer (not illustrated) disposed overthe post 125 that presses against the circuit board 64 holds the circuitboard to the post. In some versions of the invention, the function ofthe retainer is performed by a solder connection.

Control module 40 has two additional tabs 126 and 127 that supportcircuit board 64. Tab 126 is mounted to the inside of front plate 92between the two openings 107. Tab 127 is located at the corner formed bythe junction of top plate 94 and back plate 98. Both tabs 126 and 127are provided with posts 130 over which the circuit board 64 and to whicha circuit board-securing fastener is attached. Alternatively, thecircuit board is soldered to tabs 126 and 127.

A push pad 131 is mounted to the outer face of the back plate 98adjacent top plate 96. When surgical tool 30 is assembled, a set screw(not illustrated) extends from the tool housing 32 against the push pad131 to facilitate in the positioning of the control module 40. Push pad131 services as a reinforcing member that distributes the force imposedby the set screw.

A tab 99 extends perpendicularly outwardly from back plate 98. The tab99 is adjacent bottom plate 96. The tab 99 is formed with an opening,not identified. Tab 99 serves as a bracket for receiving a fastener (notillustrated) used to hold the console in the handle 38.

FIG. 4B illustrates how sensors 74 and 76, the sensors that monitor theoperation of motor 34, are mounted to the printed circuit board 64.Sensor 74, the primary sensor, is mounted in a notch 132 formed in thetop of the circuit board 64. Sensor 74 is tightly seated in notch 132.This arrangement minimizes the likelihood that, if tool 30 is subject toextreme mechanical shock, for example, dropped, the mechanical momentwill cause sensor 74 to shift relative to the motor 34. Locking of thesensor 74 in place ensures the signals generated by the sensoraccurately represent motor rotor position.

In some versions of the invention, individual pockets, indentions, areformed in top plate 94 for receiving the individual sensors 74 and 76.These pockets can be formed by half shear punching out of the workpieceforming the top plate. During assembly of the control module, eachsensor 74 and 76 is seated in the appropriate pocket. The pocketsfunctions as nests in which the individual sensors are seated. The voidspaces of the pockets also position the sensors closer to the motorrotor than if the sensors where merely disposed against the innerplanner surface of the top plate 94.

Sensor 76 is mounted to printed circuit board 64 so as to be laterallyaligned with and vertically spaced from sensor 74. In some versions ofthe invention, sensor leads 133 integral with sensor 76 (one lead shown)serve a secondary function as mounting posts that hold the sensor 76above the circuit board 64 so the two sensors 74 and 76 are aligned in aline perpendicular to both the plane and longitudinal axis of thecircuit board 64. For reasons apparent below, minor position shifts ofsensor 76 will not adversely affect operation of the surgical tool 30.

A detailed explanation of how FETs 82 a-82 c and 84 a-84 c are securedto mounting plate 119 is now provided by reference to FIG. 5. Asmentioned above, mounting plate 119 functions as both the supportstructure for FETs 82 a-82 c and 84 a-84 c and the heat sink for thethermal energy generated by these and certain other components.Copper/molybdenum laminate structures 138 a and 138 b are bonded,respectively, to the opposed top and bottom faces of plate 119.Insulating layers 140 a and 140 b are disposed over thecopper/molybdenum layers 138 a and 138 b, respectively. In actuality,copper/molybdenum layers 139 a and 139 b are bonded to the faces oflayers 140 a and 140 b, respectively, which are bonded to coppermolybdenum layers 138 a and 138 b. This means a copper-molybdenumlaminate 139 a or 139 b is soldered brazed or otherwise secured to eachcopper/molybdenum laminate layer 138 a or 138 b of the mounting plate119. This ensures that interfaces components of mounting plate 119 andinsulating layers 140 a and 140 b have identical thermal coefficients ofexpansion.

A copper/molybdenum laminate trace layer 142 is applied to the exposedface of insulating layer 140 a. The high side FETs 82 a, 82 b and 82 care attached to the exposed face of insulating layer 140 a. Wires 143and the FET leads 83 establish the electrical connections between theFETs 82 a, 82 b and 82 c and the individual traces. L-shaped brackets144 (one shown) are mounted over the traces of layer 142 at the upperend of the insulating layer 140 a, the end directed towards module topplate 94. Brackets 144 are the structural elements to which wires thatelectrically connect traces on circuit board 64 to the traces of layer142 are connected (wire connections not shown). L-shaped brackets 145(one shown) are mounted over the traces of layer 142 at the bottom endof the insulating layer 140 a, the end adjacent module bottom plate 96.Brackets 145 are the conductive components through which signals areexchanged with driver/signal pin assembly pins 113.

A set of filter capacitors 150, (one shown) are also disposed over thetraces of layer 142. Filter capacitors 150 remove AC components from theoutput signal from battery 42. The filter capacitors 150 are disposedover a common insulating layer 148 also formed of a ceramic material.Copper-molybdenum trace layers 147 and 149 are disposed, respectively,on the lower and upper surfaces of insulating layer 148. The traces ofthe lower layer 147 establish electrical connections with the physicallyadjacent traces of layer 142. The traces of upper layer 149 provide theelectrical connections to capacitors 150. Not shown are the vias throughinsulating layer 148 that connect the traces of layers 147 and 149.

The exposed face of insulating layer 140 b, the face directed towardslid 104 in FIG. 5A, is provided with a copper molybdenum trace layer152. Low side FETs 84 a, 84 b and 84 c are disposed over the exposedface of insulating layer 140 b and the traces of layer 152. Conductors153 establish connections between the FETs 84 a-84 c and the traces oflayer 152. In some versions of the invention, plural conductors 153extend from the exposed face of each FET 84 a-84 c, which is the FETsource to an adjacent trace of layer 152. The plural conductors 153establish a common ground plane for the FETs 84 a-84 c.

Also mounted to the exposed face of insulating layer 140 b and over theconductive traces of layer 152 are current sense FETs 336 a, 336 b and336 c, (one shown). Wires 154 connect the leads of the current senseFETs 336 a-336 c to the traces of layer 152. L-shaped brackets 154 (oneshown) are disposed over the traces of layer 152 at the bottom end ofthe insulating layer 140 b. Brackets 154 are the conductive componentsthrough which signals are exchanged with driver/signal pin assembly pins113.

Copper molybdenum layers 138 b and 139 b, insulating layer 140 b, traceand trace layer 152 do not extend to the top end of mounting plate 119.Instead, the top end of the undersurface of plate 119, the surfacedirected towards lid 104, is exposed. During assembly of control module40, the bottom end of circuit board 64 is placed over this exposedsurface of plate 119. This end of plate 119 is provided with twomounting pins 156, (one shown). When printed circuit board 64 ispositioned on plate, 119, pins 156 seat in openings formed in thecircuit board, (openings not identified). Lock pin retainers 157 (oneshown) fitted over the circuit board 64 and around the pins 156 hold thecircuit board in position. In some versions of the invention, solder isemployed to secure circuit board 64 to pins 156. This eliminates theneed to provide the retainers.

A U-shaped connector bracket 160 is mounted over each driver/signal pinassembly pin 113. Shown in cross section in FIG. 5 is the opening formedin the center web of the bracket 160 in which the pin 113 is press fitor otherwise conductively secured (opening not identified). Bracket 160is formed to have opposed, parallel, upwardly extending legs 161. Afirst one of the legs 161 extends above trace layer 142 and terminatesclose to one of the filter capacitors 150. The opposed leg 161 of eachbracket extends over trace layer 152.

The two spaced rows of pins 113 and the brackets 160 are shaped suchthat each bracket 160 can be used to establish the conductiveconnections pins 113 in either the upper row or lower row. Thus, thebracket 160 shown in cross section in FIG. 5 can be placed over theupper of the two pins in the Figure, rotated from 180°, and its legs 161will then be appropriately positioned.

The free end of each leg 161 is formed with a center opening 162 (FIG.3D). When control module 40 is assembled, each leg opening 162 disposedover trace layer 142 seats over the adjacent one of the brackets 145.Each leg opening 162 disposed over trace layer 152 seats over theadjacent one of the brackets 154.

C. Electrical Features

FIGS. 6A-6E illustrate the circuit internal to control module 40 thatregulates actuation of the motor 34. In general, the signals produced bysensors 66-76 are applied to a processor, in FIG. 6A, a digital signalprocessor (DSP) 170. Based on the signals generated by sensors 66 and70, the DSP 170, selectively causes the circuit to transition from apower saving “sleep” mode to an “active” mode in which the circuitenergizes the motor 34. Based on the signals generated by sensors 68 and72, DSP 170 generates output signals indicating both the speed anddirection in which the motor 34 should be run. Sensors 74 and 76generate basic signals representative of position of the motor rotor 78.The DSP 170, based on these signals, generates additional signals thatindicate rotor position.

The speed and direction instruction signals and motor rotor positionsignals generated by DSP 170 are applied to a motor control chip (MCC)172. The MCC 172, based on the DSP-generated signals, selectively gatespower FETs 82 a-82 c and 84 a-84 c. The MCC 172 also monitors thecurrent drawn by the motor 34. Actuation of the motor 34 by the MCC 172is further based on the speed at which it operates and the current itdraws.

In more detail, also internal to the control module 40 are two voltageregulators 174 and 176. A first one of voltage regulators, regulator174, outputs digital Vdd signals and analog Vdda signals that aresupplied to the other components internal to module 40. In one versionof the invention, the nominal level of the Vdd and Vdda signals are at3.3 Volts. Voltage regulator 174 continually outputs the Vdd and Vddasignals regardless of the sleep/active state of the handpiece 30.Voltage regulator 176 outputs a Vcc signal applied to the othercomponents internal to the module 40. In one version of the inventionthe Vcc signal is at 12 Volts. Voltage regulator 176 is normally in adeactivated state. When voltage regulator 176 is in this deactivatedstate, the whole of the control circuit is in the sleep mode. Only whenone of the trigger switches 46 or 47 is depressed to actuate thehandpiece 30, does voltage regulator 176 transition to the active state.This transition results in the whole of the control circuittransitioning from the sleep mode to the active mode.

The positive terminal of the battery 42 is connected to both voltageregulators 174 and 176. In the illustrated version of the invention, thebattery positive terminal is connected to a forward biased diode 177.The cathode of diode 177 is connected to two parallel connectedresistors 178 and 180. The signal present at the opposed junction ofresistors 178 and 180 is applied to both voltage regulators 174 and 176as the Vin signal. In some versions of the invention, a single resistorperforms the function of resistors 178 and 180. In the application, thevoltage present at the positive terminal of battery 42 is the BATT+signal.

In one version of the invention, an LT1765EFE-3.3 3 Amp 1.25 MHzStep-Down Switching Regulator available from the Linear TechnologyCorporation of Milpitas, Calif. is employed as voltage regulator 174. Acapacitor 182 is tied between the Vin input of this voltage regulator174 and ground. A capacitor 184 and series connected resistor 186 aretied between the Vc pin of voltage regulator 174 and ground. A capacitor188 is tied across capacitor 184 and resistor 186. Other groundconnections of the pins of the voltage regulator 174 to ground are notspecifically described.

The output voltage from voltage regulator 174 is obtained from the Vswpin. The output signal is applied to an inductor 190. The voltagepresent at the end of inductor 190 distal from the voltage regulator 174is the Vdd voltage. The voltage present at the distal end of inductor190 is applied through a forward biased diode 192 to the boost pin ofthe voltage regulator. A capacitor 194 is tied between the Vsw pin ofthe voltage regulator 174 and the cathode of diode 192. A rectifyingdiode 196 is forward bias connected between ground and the Vsw pin ofvoltage regulator 174. An inductor 198 is connected to the distal end ofinductor 190. The voltage present at the end of inductor 198 distal tovoltage regulator 174 is the Vdda voltage. A capacitor 202 is connectedbetween the junctions of inductors 190 and 198 and ground. The voltagepresent at the junctions of inductors 190 and 198, the Vdd voltage, isapplied back to the voltage regulator 174 as the feedback voltage.

In one version of the invention, the LT3436 3 Amp, 800 kHz, Step-UpSwitching Regulator, also from Linear Technologies, is employed asvoltage regulator 176. A capacitor 206 is tied between the ground theVin pin of voltage regulator 176. A voltage suppression diode 208 isalso tied between ground and the Vin pin of voltage regulator 176. Diode208 prevents transient voltages from being applied to the Vin pins ofboth voltage regulators 174 and 176. A capacitor 209 and seriesconnected resistor 210 are connected between the Vcc pin of voltageregulator 176 and ground. A capacitor 212 is tied across capacitor 208and resistor 210. Other ground connections to the pins of voltageregulator 176 are not discussed.

The output voltage of the voltage regulator 176 is based on the signalat the Vsw pin. This signal is applied to a capacitor 214 and a seriesconnected, forward biased diode 216. The signal present at the cathodeof diode 216 is the Vcc signal. Capacitor 217 connected between thecathode of diode 216 and ground filters AC components from the Vccsignal. The signal applied to the Vin pin of voltage regulator 176 isapplied to the Vsw pin of the voltage regulator through an inductor 218.The signal present at the junction of capacitor 214 and diode 216 istied to ground through an inductor 220. The signal present at thecathode of diode 216 is applied to ground through a voltage dividerconsisting of series connected resistors 222 and 224. The voltagepresent at the junction of resistors 222 and 224 is applied back to thefeedback pin of voltage regulator 176.

An alternative voltage regulator 176 is the LM3478MM available fromNational Semiconductor. This voltage regulator requires a separateexternal FET (not illustrated) for selectively tying inductor 220 toground.

An AWAKE signal digital signal from DSP 170 is selectively applied tovoltage regulator 176. The AWAKE signal, which is asserted high, isapplied to a SHDN pin on the voltage regulator. The assertion of theAWAKE signal actuates voltage regulator 176. The negation of the AWAKEsignal causes voltage regulator 176 to cease outputting the Vcc signal.

Sensors 66 and 70 each output a bi-state, digital signal as a functionof the proximity of the associated magnets 56 and 58, respectively. Inone preferred version of the invention, A3213LUA Hall effect switchesavailable from Allegro Microsystems of Worchester, Mass., function assensors 66 and 70. The Vdd signal is applied to the supply pin of eachsensor 66 and 70. The ground pin of each sensor 66 and 70 is tied toground. The output pins of sensors 66 and 70 are tied to a common inputpin of DSP 170. In some versions of the invention, these output pins aretied to separate input pins of the DSP 170.

Sensors 68 and 72 each output an analog signal as function of theproximity of the associated magnet 56 and 58, respectively. In oneversion of the invention, the SS495A Ratiometric Linear (Hall) sensorsavailable from Honeywell Sensing and Control of Freeport, Ill. areemployed as sensors 68 and 72. A 5 Volt signal is applied to the Vssupply pin of each sensor 68 and 72. The V-pin of each sensor 68 and 72is tied to ground. The output signals from sensors 68 and 72 are appliedto separate analog signal input pins of the DSP 170. Each output signalfrom the sensor 68 or 72 is applied to the DSP 170 through a separateresistor 230. A capacitor 232 is tied between the end of each resistor230 adjacent the DSP 170 and ground. A zener diode 233 is also tiedbetween the output pin of each sensor 68 and 72 and ground, cathodesdirected to the DSP 170. Zener diodes 233 protect DSP 170 from highvoltage signals emitted by sensors 68 and 72. These high voltage signalsmay be generated if the sensors are exposed to a reverse polaritymagnetic field.

Sensor 74 is identical to sensors 68 and 72. The Vs pin of sensor 74 istied to the 5 Volt voltage source; the V-pin is tied to ground. Theoutput signal of sensor 74 is applied through a resistor 234 to theinverting input of an amplifier 236. A capacitor 238 is tied between theinverting input of amplifier 236 and ground. Feedback to the amplifier236 is supplied by a resistor 240 tied between the output of theamplifier and the inverting input. A reference signal is applied to thenoninverting input of amplifier 236. In the illustrated version of theinvention, the reference signal is signal is supplied from the center ofa voltage divider consisting of series connected resistors 242 and 244.The free end of resistor 242 is connected to the 5 Volt source. The freeend of resistor 244 is tied to ground. Resistors 242 and 244 areselected so that reference voltage is typically between 1.5 and 3.0Volts. The output signal produced by amplifier 236 is applied to ananalog input of DSP 170.

In the illustrated version of the invention, sensor 76 is identical tosensor 74. The output signal from sensor 76 is applied through aresistor 246 to the inverting input of an amplifier 248. A capacitor 250is tied between the inverting input of amplifier 248 and ground. Aresistor 252 tied between the output of amplifier 248 and the invertinginput supplies the feedback. The reference signal applied to thenoninverting input of amplifier 236 is supplied to the noninvertinginput of amplifier 248. The output signal generated by amplifier 248 isapplied to a distinct analog input of DSP 170.

In one version of the invention, amplifiers 236 and 248 are both formedfrom MAX4247 Ultra-Small, Rail-to-Rail I/O With DisableSingle/Dual-Supply, Low-Power Operation Amplifier available from theMaxim Company of Sunnyvale, Calif. Not shown are where the Vdd signal isapplied to each amplifier 236 and 248. Also, a capacitor, (notillustrated) is tied between the Vdd pin of amplifier 236 and ground.LMV982 amplifiers available from National Semiconductor may also be usedas amplifiers 236 and 248.

Amplifiers 236 and 248 each have a SHDN pin to which an activationsignal is selectively applied. The AWAKE signal from the DSP 170 isselectively applied to the SHDN pins to regulate the on/off state of theamplifiers 236 and 248.

In one version of the invention the MC56F8322 16-Bit Hybrid Controllerfrom Freescale Semiconductor of Chandler, Ariz. is employed as the DSP170. DSP 170 powered by the Vdd and Vdda signals. Not shown are thecapacitors that filter the Vdd and Vdda signals applied to the DSP 170.DSP 170 receives as inputs the above five described signals from sensors66-76. DSP 170 also monitors the filtered voltage out of battery 42.Specifically, the BATT+ signal is applied to an analog input pin of theDSP 170 through a voltage divider consisting of series connectedresistors 258 and 260. The BATT+ signal is applied to the free end ofresistor 258. The free end of resistor 260 is tied to ground. Acapacitor 262 is tied across resistor 260. The voltage present at thejunctions of resistor 258 and 260 is applied to an analog input pin ofDSP 170. Capacitor 260 thus filters the divided down BATT+ signal beforeit is applied to the DSP 170 for monitoring.

The DSP 170 also receives as an input an indication from the MCC 172when the motor 34 draws an excessive amount of current. Specifically,the MCC 172 generates a maximum current (I_LMT) signal to the DSP 170when the current drawn by motor 34 exceeds a set amount.

DSP 170 outputs five signals. The first signal output is the AWAKEsignal. The AWAKE signal is asserted when the DSP 170 receives a signalfrom either sensor 66 or sensor 70 that the magnet 56 or 58,respectively, associated with the sensor is proximally displaced fromthe most distal position. This signal represents the depression of theassociated trigger switch 46 or 47 to actuate the handpiece 30.

The second and third signals output by DSP 170 are respectively, FORWARD(FWD) and REVERSE (REV) signals. These signals are output as a functionof the output signals generated by sensors 68 and 72. Generally theactuation of a separate one of the trigger switches 46 or 47 results inthe outputting of a separate one of the FORWARD or REVERSE signals. THEFORWARD and REVERSE signals are applied to the MCC 172.

As explained below, though, there is no set relationship between whichtrigger switch 46 or 47 is depressed to cause a specific one of theFORWARD or REVERSE signals to be output. Depending on how the handpiece30 is selectively configured, one presses either one of the triggerswitches 46 or 47 to cause the FORWARD signal to be output. Similarly,based on the temporary configuration of the handpiece 30, in order tocause the REVERSE signal to be asserted, either trigger switch 46 or 47is depressed. Depending on handpiece configuration, simultaneousdepression of the both trigger switches 46 and 47 can result insimultaneous assertion of the FORWARD and REVERSE signals. Handpiece 30may further be configured so that depression of one of the triggerswitches 46 or 47 causes the FORWARD and REVERSE signals to besimultaneously asserted.

The fourth signal output by DSP 170 is a set of Hall signals, HALLxsignals in the Figures, representative of signals representative of theangular position of the motor rotor 78. The HALLx signals are equivalentto the signals generated if traditional digital Hall sensors mounted inthe motor 34 generate signals representative of rotor position. DSP 170normally outputs the HALLx signals as a function of the signal receivedfrom sensor 74. At start-up, the output HALLx signals are further afunction of the signal output by sensor 76. The HALLx signals areapplied to the MCC 172.

The fifth signal output by DSP 170 is a USER_SPEED (U_S) signal. TheUSER_SPEED signal is generated as a function of the signal received fromthe sensor 68 or 72 associated with the most fully depressed triggerswitch 46 or 47, respectively. In the described version of theinvention, the USER_SPEED signal is an analog signal. The process stepsDSP 170 executes in order to, based on the signal from the sensor 68 or72, generate the USER_SPEED signal are discussed below.

Motor control circuit 172 is an application specific integrated circuit.Generally, MCC 172 based on states of the FORWARD, REVERSE, USER_SPEED,and HALLx signals, generates the signals necessary to gate FETs 82 a-82c and 84 a-84 c to cause the appropriate actuation of the motor 34. Adetailed understanding of the motor control sub-circuits internal to MCC172 is obtained from the Applicant's U.S. Pat. No. 6,025,683, MOTORCONTROL CIRCUIT FOR REGULATING A DC MOTOR, issued 15 Feb. 2000, thecontents of which are incorporated herein by reference.

While a detailed understanding of a number of the sub-circuits internalto MCC 172 is provided in U.S. Pat. No. 6,025,683, the followingunderstanding of the MCC 172 is provided by reference to FIGS. 6B and 7.

One sub-circuit internal to the MCC 172 is the direction controller 270.Direction controller 270 is the MCC 172 sub-circuit that receives theFORWARD and REVERSE signals from the DSP 170. As a function of theFORWARD and REVERSE signals, direction controller 270 selectivelyasserts a FORWARD/REVERSE (F/R) signal. If the FORWARD and REVERSEsignals from the DSP 170 are simultaneously asserted, directioncontroller 270 cyclically asserts and negates the FORWARD/REVERSEsignal. This, in turn, causes energization signals to be applied to themotor 34 so that rotor 78 oscillates back and forth.

Direction controller 270 includes a FET 272. The drain of FET 272 istied to a resistor 344, (FIG. 6D) that is part of an off-chip currentmeasuring circuit. As discussed below, the current measuring circuitgenerates a variable signal as a function of the current drawn by themotor 34. The source of FET 272 is tied to ground. Normally, directioncontroller 270 maintains FET 272 in an on state. When the motor is to bedriven in an oscillator pattern, direction controller 270 alsoperiodically gates FET 272 off. As discussed below, this causes themagnitude of the signal representative of the current drawn by motor 34to change.

A tachometer 274 is also internal to the MCC 172. The tachometer 274receives as input signals the HALLx signals from the DSP 170. Based onthe HALLx signals, the tachometer 274 produces a constant on time pulseas a tachometer signal (TACH). The frequency with which the pulses aregenerated is representative of the rotational speed of motor 34.

The MCC 172 also includes a speed controller 276. The speed controller276 receives as inputs the USER_SPEED signal and the TACH signal. Basedon these signals, speed controller 276 produces a pulse width modulatedSPEED_CONTROL (S_C) signal. Specifically, the USER_SPEED signal isapplied from DSP 170 through a resistor 278, seen in FIG. 6B, to thespeed controller 276. A capacitor 280 is tied between the MCC 172 pinthrough which the USER_SPEED signal is input and ground.

Internal to the speed controller 276 is an operational amplifier, notillustrated. The USER_SPEED signal is applied to the noninverting inputof this amplifier. The TACH signal is applied to the inverting input ofthe amplifier. This signal is applied to the amplifier through anoff-chip resistor 282. The output signal of this amplifier is alsoapplied as a feedback signal to the amplifier inverting input. Thissignal is feedback through a resistor 284. A capacitor 286 is tiedacross resistor 284. A DC voltage is also applied to the inverting inputof the speed control operational amplifier. This voltage is taken from avoltage divider consisting of series connected resistors 288 and 290.The free end of resistor 288 is connected to the 5 Volt supply. The freeend of resistor 290 is tied to ground. The voltage present at thejunction of resistors 288 and 290 is applied to the inverting input ofthe speed controller amplifier through a resistor 292. This amplifierand the other components of speed controller 276 cooperate to generate aSPEED_CONTROL (S_C) signal. The SPEED_CONTROL signal is a pulse widthmodulated signal. The on duty cycle of the SPEED_CONTROL signal isproportional to the difference between the user-selected speed and themeasured speed of the motor 34.

Speed controller 276, also selectively asserts a digital BRAKE_ENABLE(B_E) signal. The BRAKE_ENABLE signal is asserted whenever the outputsignal from the operational amplifier indicates the motor rotor 78 isturning at a rate significantly greater than the user-desired speed.

In FIG. 7, the BRAKE_ENABLE signal is shown as being applied directly toa motor drive circuit 298. This is for purposes of simplicity. Inpractice, the BRAKE_ENABLE signal may be applied to the directioncontroller 270. The direction controller 270 serves as the actualsub-circuit that asserts the BRAKE_ENABLE signal to the motor drivecircuit 298. This construction makes it possible for the directioncontroller 270 to, when the motor 34 is to be driven in oscillatorymode, cyclically assert the BRAKE_ENABLE signal. This reduces toolvibration when motor 34 is oscillated.

A current monitor 296, again part of the MCC 172, monitors the currentdrawn by the motor 34. Current monitor 296 is essentially a comparator.When the current limit exceeds a set limit, current monitor 296 assertsa current limit (I_LMT) signal. This I_LMT signal is the signal assertedto the DSP 170.

The motor drive circuit 298, also integral with the MCC 172 asserts thebasic trigger signals that gate FETs 82 a-82 c and 84 a-84 c. Motordrive circuit 298 receives as input signals, the S_C signal, the F/Rsignal, the BRAKE_ENABLE signal, the HALLx signals and I_LMT signal.Based on these signals motor drive circuit 298, asserts three (3) highdrive H_D signals and three (3) low drive L_D signals. The H_D signalsare asserted to individually gate FETs 82 a-82 c, the FETs that tie thewindings 86 a-86 c, respectively, to the BATT+ voltage. The L_D signalsare asserted to individually gate FETs 84 a-84 c, the FETs that tie thewindings 86 a-86 c, respectively, to the BATT− ground.

Motor control circuit 172 also includes high side drivers 302 and lowside drivers 304. Each H_D signal is applied to a specific one of thehigh side drivers 302, collectively shown as a single block. Each highside driver 302, in response to receipt of the associated H_D signal,asserts a high side control (Hx) signal to the gate of associated one ofthe FETs 82 a, 82 b or 82 c. Each Hx high side control signal is appliedto the associated FET 82 a, 82 b or 82 c through a distinct conductor308.

The actual H1, H2 or H3 signal applied to each FET 82 a, 82 b or 82 c,respectively, is applied to the FET's gate through a resistor 315. Thedrain of each FET 82 a-82 c is tied to the BATT+ terminal of the battery42. The source of each FET 82 a, 82 b and 82 c is tied to a separate oneof the windings 86 a, 86 b and 86 c.

A boost signal from a flyback circuit is applied to the gates of FETs 82a, 82 b and 82 c to ensure they are forward biased relative to thecomplementary sources. Each flyback circuit consists of a diode 310 towhich the Vcc signal is applied. This signal is applied to a capacitor312. The opposed end of the capacitor is tied to the winding to whichthe associated FET 82 x is attached. In FIGS. 6B, 6C and 6D, the M1, M2,M3 conductors are shown extending to windings 86 a, 86 b and 86 c,respectively. A zener diode 314 is reverse bias connected between eachHx line and the associated Mx line.

A boost circuit, part of the flyback circuit and contained in the highside drive circuit 302, triggers the outputting of the boosted gatesignal. Specifically, when each winding 86 a, 86 b, or 86 c is tied toground, charge builds across the associated capacitor 312. Capacitor312, it is further observed, is connected to the high side circuit 302through a CFLYx connection. The boost circuit internal to the high sidedrive circuit includes a FET, not illustrated, for regulating currentflow from the capacitor. The signals on the Mx line serve as thereference signals for the boost circuit. When the winding is to be tiedto the BATT+ terminal, the charge across the capacitor 312 is appliedthrough the CFLYx connection and turned on boost circuit FET. Thisboosted signal is then output over Hx line to the gate of theappropriate FET 82 a, 82 b or 82 c. Diodes 314 prevent burn out of theassociated FET 82 a, 82 b or 82 c if the gate to source voltage exceedsa specific level. In one version of the invention, this is 15 Volts.This prevents possible FET burnout due to the rotor being stalled. Inthis situation, there will not be any back EMF signals on the windings.In this situation, the voltage present at the sources of the FETs 82 xcan drop to near zero.

Each LD signal is applied to a specific one of the low side drivers 304,collectively shown as a single block. When an LD signal is applied to alow side driver 304, the driver 304 asserts a low side control signal(Lx) to the gate of the associated FET 84 a, 84 b or 84 c. Each low sidedrivers 304 include a pair of series connected off-chip FETs, notillustrated. The drain of a first one of the FETs is tied to the Vddvoltage source. The source of the second FET is tied to an off chipKelvin ground 318 (Conductor represented as KGND). The signal present atthe junction of the source of the first FET to the drain of the secondFET is the Lx low side control signal. The sources of the FETs 84 a-84 cthat tie the windings 86 a-86 c to ground are also connected to Kelvinground by a conductor 320.

The Lx signals asserted by each low side driver 304 are applied to thegate of a separate one of the FETs 84 a, 84 b or 84 c through a resistor321. The drain of each FET 84 a, 84 b and 84 c is tied to a separatewinding 86 a, 86 b and 86 c, respectively. The sources of FETs 84 a-84 care tied to the BATT− pin, the terminal to where the negative terminalof the battery 42 is connected.

Also internal to MCC 172 is a bandgap circuit 322. Bandgap circuit 322functions as a temperature independent constant voltage source and aconstant current source for the components internal to the MCC 172.

While not illustrated, it should be understood that MCC has 5 Voltregulated voltage source. This voltage source functions as the 5 Voltpower supply for the other components internal to control module 40including sensors 68, 72, 74 and 76, connections not shown. The outputsignal from this voltage regulator is applied to ground through seriesconnected resistors 324, 326 and 328 seen in FIG. 6B. The voltagepresent at the junction of resistors 324 and 326 is applied to the speedcontroller 276 as a brake reference (BRK_REF) signal upon which theassertion of the BRAKE_ENABLE signal is based. The voltage present atthe junction of resistors 326 and 328 is applied the current monitor 296as a reference (I_REF) signal upon which the assertion of the I_LMTsignal is based.

A capacitor 329 is in parallel across resistors 324, 326 and 328 andground. The voltage present at the junction of resistor 324 andcapacitor 329 is the filtered, voltage regulated 5 Volt referencesignal.

A more detailed understand of the above circuits is presented in theaforementioned, incorporated by reference U.S. Pat. No. 6,025,683. Inthe circuit disclosed in this document, the bandgap regulator alsofunctions as the 5 Volt regulated power supply.

The MCC 172 is powered by the Vcc signal produced by voltage regulator176. The Vcc signal is applied to separate Vcc and DRVcc pins on the MCC172. A capacitor 330 is tied between the Vcc pin and ground. Acomplementary analog ground pin on MCC 172 is tied to the ground ofcapacitor 330. A capacitor 332 is tied between the DRVcc pin and ground.A complementary digital ground pin on MCC 172 is tied to the ground ofcapacitor 332. The Vcc signal is also applied to a Vmm pin on MCC 172through a resistor 333

As mentioned above, the control module 40 also includes a circuit formonitoring the current drawn by the motor 34. This circuit includesthree FETs 336 a, 336 b and 336 c. The drain of each FET 336 a, 336 band 336 c is tied to a separate one of the motor windings 86 a, 86 b and86 c, respectively. The L1, L2 or L3 low side control signals applied tothe gate of each FET 84 a, 84 b or 84 c, respectively, are applied tothe gate of the complementary FET 336 a, 336 b or 336 c, respectively.Thus, each time a FET 84 a, 84 b or 84 c is turned on, the complementaryFET 336 a, 336 b or 336 c, respectively, is likewise turned on.

The sources of FETs 336 a-336 c are connected to a common resistor 338.The free end of resistor 338 is tied to ground through a resistor 340.The voltage present at the junction of resistors 338 and 340 is appliedto the MCC current monitor 296 as MTR_I signal representative of currentdrawn by the motor 34. A capacitor 342 connected across resistor 340filters this signal

Resistor 344 is also connected at one end to the junction of resistors338 and 340. The second end of resistor 344 is connected to the drain ofFET 272. Normally, when FET 272 is gated on, the signal across resistor338 flows to ground through the parallel paths of resistor 340 and 344.Thus, normally, the MTR_I signal is based on a relatively lowvolts/current ratio.

When the motor 34 is driven in an oscillatory mode, direction controller270 gates FET 272 off for an initial period of time after theFORWARD/REVERSE is toggled. This effectively disconnects resistor 344from the current measuring circuit. The MTR_I signal is then based onrelatively high volts/current ratio. This, in turn, causes the currentmonitor 296 to assert the I_LMT signal more rapidly than it wouldotherwise be asserted. The rapid assertion of the I_LMT signal, in turn,causes the less frequent application of energization signals to themotor 34. This reduces initial motor acceleration. The reduction ofmotor acceleration, in turn, reduces the counter torque the handpiece 30initially produces. This “counter-torque” is torque opposite the torquethe handpiece produces as a consequence of the motor rotating in a firstdirection. The minimization of the counter torque reduces the kick thehandpiece produces in the hand of the user as the motor shifts rotationfrom a first direction to a second direction.

D. Tool Operation

The operation of surgical tool 30 of this invention is now explained byreference to the flow chart of FIGS. 8A-8D. Prior to actuation of thehandpiece 30, the DSP 170, in step 360, is provided with instructionsthat identify the command signals each trigger switch 46 and 47 are togenerate. For example, based on surgeon preference, either triggerswitch 46 or 47 is set to be the switch that is depressed to cause thehandpiece motor to run in the forward direction. The remaining triggerswitch 47 or 46 is set to be the one depressed to run the switch in thereverse direction.

Alternative trigger switch settings are possible. For example, onetrigger switch 46 or 47 may be set so that its depression causes themotor to run in the forward direction; the second trigger switch 47 or46 is set so that its depression causes the motor to run oscillatorypattern. In still another configuration, the handpiece 30 is set so thatdepression of either trigger switches 46 or 47 causes the motor to runin the forward direction. As discussed below, the handpiece may be soset so that full depression of switch 46 causes motor 34 to run at afirst speed; full depression of switch 47 causes motor 34 to run at asecond speed. In another alternative configuration, the handpiece 30 isset so that depression of one trigger switch 46 or 47 causes the motorto run in the forward or reverse direction. In this configuration, thesecond trigger 47 or 46 switch is set to an inactive state; depressionof this switch does not result in any actuation of the handpiece motor34.

Thus step 360 is the loading into the DSP 170 instructions indicatingwhich signal, FORWARD, REVERSE or oscillation between the two, the DSPshould generate upon detection that a particular trigger switch 46 or 47is depressed.

Prior to operation of the handpiece 30, in step 362, the DSP 170 is alsoloaded with instructions indicating the range of the USER_SPEED signalthat is to be generated as a function of the extent to which thespecific trigger switch 46 or 47 is depressed. This range is a functionof variables such as surgeon preference, type of cutting accessoryattached to the handpiece, and type of the surgical procedure beingperformed. For example, based on the preferences of one surgeon, thetrigger switches may be set so that trigger switch 46 is the switch thatis depressed to cause the motor to run in the reverse direction and whenthe switch is fully depressed the motor will run at a maximum of 25,000RPM. The same surgeon sets DSP 170 so that full depression of triggerswitch 47 causes the motor 34 to run in the reverse direction and themaximum speed the motor will run when so actuated is 15,000 RPM.

A second surgeon sets DSP 170 so that depression of either triggerswitch 46 or 47 causes the motor to run in the forward direction. Thissurgeon more specifically sets handpiece 30 so that when trigger switch46 is fully depressed, the motor runs at a maximum of 30,000 RPM and,when trigger switch 47 is fully depressed, the motor runs at a maximumof 7,500 RPM.

Also, as part of step 362, the minimum speed at which the motor 34 isrun may also be actuated. Thus, a surgeon may set the handpiece so thatwhen one of the trigger switches 46 or 47 is actuated, the motor runs inthe forward direction at speeds between 5,000 and 25,000 RPM. When thesecond trigger switch 47 or 46 is depressed, the motor 34 runs in theforward direction at speeds between 10,000 and 13,000 RPM.

Steps 360 and 362, it should be recognized, are only performed if aparticular surgeon wants to operate the handpiece in mode different fromthe mode defined by the default settings previously stored in the DSP170. Typically, these default settings are loaded into the DSP 170during the manufacturing process.

Prior to actual use of the handpiece, the DSP 170 maintains thecomponents internal to control module 40 in the sleep mode. The AWAKEsignal is not asserted. Thus, voltage regulator 176 does not output theVcc signal. Since the Vcc signal is not output, the MCC 172 is in adeactivated state. Since the MCC 172 is deactivated, the MCC voltageregulator does not output the 5 Volt signal to the components to whichit is otherwise applied. Sensors 68, 72, 74 and 76 are, therefore,inactive. Also deactivated are the analog to digital converters internalto the DSP 170 (converters not illustrated).

Even when the surgical tool 30 is in the sleep mode, voltage regulator174 outputs the Vdd and Vdda signals. Sensors 66 and 70 and DSP 170 arethus active even when the above-discussed tool components are in thesleep mode.

Depression of one of the trigger switches 46 or 47, step 364, results inthe actuation of the handpiece 30. For purposes of illustration,discussion proceeds with the understanding that trigger switch 47 is thedepressed switch. Initially, the movement of trigger switch 47, actuallymagnet 58, is detected by sensor 68, step 366. Consequently, in step366, the output signal generated by sensor 68 undergoes a state change.DSP 170, upon detecting the change in state of the output signal fromsensor 68, asserts the AWAKE signal, step 368.

Upon the assertion of the AWAKE signal 368, in a step 370, the remainderof the handpiece 30 enters the active mode. Specifically, the assertionof the AWAKE signal causes voltage regulator 176 to start to output theVcc signal. The receipt of the Vcc signal energizes MCC 172. As aconsequence of this energization, the MCC voltage regulator outputs the5 Volt signal to the other components of the module 40 including sensors68, 72, 74 and 76. Another sub-process of the sleep-to-active transitionis the activation of the analog to digital converter block internal tothe DSP 170.

As part of step 370, the AWAKE signal is also applied to the SHDN pinsof amplifiers 236 and 246. Amplifiers 236 and 246 are thus enabled toproduce amplified versions of the output signals generated by sensors 74and 76, respectively. In practice it takes the components internal tocontrol module 40 approximately 200 msec or less to transition from thesleep mode to the active mode. In more preferred versions of theinvention, it should take 100 msec or less to undergo the transition.This is to minimize the extent to which the user may perceive a delay intool start up.

Once the control module components are in the active mode, sensor 72asserts a variable output signal based on the detected movement ofmagnet 58, step 372. Based on receipt of the signal from sensor 72, theDSP 170 engages simultaneously in steps 374 and 376. In step 374, basedon the instruction data loaded in step 360, DSP 170 asserts theappropriate state FORWARD or REVERSE signal or a combination of thesesignals. If the handpiece 30 is set so that trigger switch 47 is theforward control switch then, in step 374, the DSP asserts the FORWARDsignal. If trigger switch 47 is set to be the reverse control switch,the DSP asserts a REVERSE signal. Alternatively, if trigger switch 47 isset as the oscillating control switch, DSP 170 simultaneously assertsboth the FORWARD and REVERSES signals.

In step 376, the DSP 170 generates the USER_SPEED signal. This signal isbased on the instructions received in step 362 and the signal fromsensor 72 representative of the extent to which magnet 58 has beendisplaced along its path of travel. When DSP 170 is programmed to varythe USER_SPEED linearly with the extent to which trigger switch 47 isactuated, the signal is determined according to the following formula

USER_SPEED=SPD_(MIN)+SS(SPD_(MAX)−SPD_(MIN))  (1)

Here SPD_(MIN) and SPD_(MAX) are, respectively, the minimum and maximumspeeds the motor 34 is to be run when trigger switch 47 is depressed.These are the coefficients supplied in step 362. The variable SS is thesensor signal from sensor 72, normalized from 0.00 to 1.00,representative of the extent to which trigger switch 47 is displacedfrom the extended to the retracted position.

As discussed below DSP 170 may be programmed to vary USER_SPEED in otherthan a linear relationship based on the displacement of the triggerswitch.

In a step 378, which occurs near simultaneously with steps 374 and 376,the DSP 170 also generates HALLx signals representative of the positionof the motor rotor 78. At start up, rotor speed 0 RPM, these data arebased on signals from both sensor 74 and sensor 76. The basis for thisdetermination is now explained by reference to the plots in the graph ofFIG. 9. This graph illustrates the signals generated from the sensors 74and 76 if the rotor is a two pole rotor. This is for the purposes ofsimplification. Thus, the output signal from sensor 74, plot 382, is asingle sine wave over the 360° of rotation of the rotor.

In order for the MCC 172 to generate the Hx and Lx control signals inthe appropriate sequence on motor start-up, the HALLx supplied from theDSP 170, must indicate within which sextant, 60° arc, the rotor 78 islocated. If the signal from sensor 74 is between 0.866 and 1.00 it isclear that rotor is within the arcuate range of 60 to 120°. Similarly,if the signal from sensor 74 is between −0.866 and −1.0, it is clearthat the rotor is within the arcuate range of 240 to 300°.

However, outside of these ranges, the single signal from sensor 74 doesnot, at start-up, accurately indicate rotor position. This is becauseoutside of these two ranges, the single signal does not indicate whereon the sine wave curve the rotor is located. For example, if the signalgenerated by sensor 74 is 0.5, it is not clear if the rotor is at the30° position or the 150° position. On plot 382, these two positions arerepresented by points 384 and 386, respectively. Similarly, if thesignal from sensor 74 is −0.71 it is not clear if the rotor is at the225° position or the 315°. On plot 382 these two positions arerepresented by points 388 and 390, respectively.

Thus, at start-up, in step 378, the DSP 170 employs the signals fromboth sensors 74 and 76 to generation an accurate determination of rotorposition. In the illustrated version of the invention, since sensor 76outputs an analog signal, this sensor is positioned in control module 40to output a signal that is a maximum 60° out of phase behind the signalgenerated by sensor 74. In FIG. 9, the normalized signal output bysensor 76 is shown as plot 391.

In step 378, when the signal from sensor 74 outside of the ranges inwhich this signal alone can be used to determine rotor position one oftwo evaluations are performed. If the normalized output signal fromsensor 74 indicates the rotor 78 is in either that 0 to 60° sextant orthe 120 to 180° sextant, a test is made to determine if:

sensor 74 signal>sensor 76 signal

If this determination tests true, then, collectively the sensor signalsindicate the rotor is in an angular position between 0 and 60°. If thisdetermination tests false, collectively the signals indicate the rotoris in a position between 120 and 180°. If the normalized output signalfrom sensor 74 indicates the rotor is in either the 180 to 240° sextantor the 300 to 360° a test is made to determine if:

sensor 74 signal<sensor 76 signal

If this determination tests true, then, the sensor signals indicate therotor is in an angular position between 180 and 240°. If thisdetermination tests false, then the rotor is in a position between 300and 360°.

Thus, on start-up, based on the signal from sensor 74 and the comparisonof the signals generated by sensors 74 and 76, the DSP 170 generates aHALLx signals representative of motor rotor position.

Consequently, immediately after start-up, DSP 170 presents the followingsignals to MCC 172: the FORWARD and/or REVERSE signals; a USER_SPEEDsignal; and HALLx signals. Based on these signals, MCC 172 asserts theHIGH_ and LOW_SIDE_CONTROL signals. These signals are asserted in thesequence necessary to cause the energization currents to be applied tothe windings in the appropriate pattern needed to cause the rotor 78 tobe rotated in the appropriate user-selected direction and at theappropriate user-selected speed.

Based on the above signals, in step 393, MCC appropriately gates FETs 82a-82 c and 84 a-84 c to cause the energization signals to be applied tothe windings 86 a-86 c so that rotor 78 turns in the appropriatedirection.

As energization signals are applied to the windings, the rotor 78rotates. Once the initial position of the rotor 78 is determined, thelater positions of the rotor 78 are determined solely on the basis ofthe signal produced by sensor 74. DSP 170 converts this signal intosubsequent sets of HALLx signals. Based on the state of the HALLxsignals, MCC 172 continues to assert the HIGH_ and LOW_SIDE_CONTROLsignals needed to cause the rotor to turn in the user-desired directionat the user-desired speed.

The means by which the HALLx signals are subsequently determined isdescribed by reference to waveform 402 of FIG. 10 and the flow chart ofFIGS. 11A-11D. Waveform 402 represents the output signal from sensor 74over a complete 360° of rotation of rotor 78. Since rotor 78 is a sixpole rotor, over the course of the complete rotation, sensor 74generates three sine waves. In FIG. 10, the three peak values are thevalues at points 406 a, 406 b and 406 c. The three valley values are thesignal levels at points 408 a, 408 b and 408 c. In FIG. 10, theindividual sine waves are shown as having identical peak and valleysignal levels. It should be understood that, in actuality, even at avery cold or very hot start-up, there are some differences in thesesignal levels. These differences though are typically less than 5%.

During manufacturing calibration, a non-volatile memory 404 integralwith DSP 170, represented by FIG. 12, is loaded with data representingthe peak and valley point values of the output signal from sensor 74. Asingle start-up peak value is stored in field 410. A single start-upvalley value is stored in a field 412. In some versions of theinvention, the single start-up peak value is the largest of the threepeak values at points 406 a, 406 b or 406 c. The single start-up valleyvalue is the value lowest of the three valley values 408 a, 408 b or 408d. In an alternative version of the invention, the stored start up peakvalue is the average or median of the three peak values 406 a, 406 b or406 c. In these versions of the invention, the stored valley value infield 412 is the average or median of the three valley values 408 a, 408b or 408 c.

Prior to sensor 74 generating the output signal representing thetransition from one peak to the next valley (or one valley to the nextpeak) DSP 170 performs signal processing to determine when the state ofthe HALLx signals are to be changed. Specifically in a step 416, for thesignals from peak 406 a to valley 408 a, DSP 170 determines thedifference value, A, between the peak and the valley. This value isdetermined by the formula:

Δ=SIGNAL VALUE^(PEAK)−SIGNAL VALUE^(VALLEY)  (2)

In a step 418, a midpoint value, MP, between the peak 406 a and valley408 a is determined according to the following formula:

MP=Δ/2+OFFSET  (3)

Here, OFFSET is the level of the sensor signal at the valley 406 a, theSIGNAL VALUE^(VALLEY) signal. In FIG. 10, this midpoint reference signallevel is represented by point 420 a. At least, immediately afterstartup, it should be understood that the SIGNAL VALUE^(PEAK) and SIGNALVALUE^(VALLEY) values are the signal levels retrieved from memory 404.

In steps 422 and 424 the DSP 170 determines, respectively, the upper andlower transitions for the signal from sensor 74. In step 422, the uppertransition is determined according to the formula:

UPPER TRANS=MP+0.433Δ  (4)

In step 424, the lower transition is determined according to theformula:

LOWER TRANS=MP−0.433 Δ  (5)

In Equations (4) and (5), the constant 0.433 is based on the fact that,in this version of the invention, the HALLx signal transitions are tooccur at each 60° phase change of waveform 402. The first phasechange/HALLx signal transition occurs as the waveform changes from the359° to 0° position. Therefore, the next HALLx signaltransition-inducing phase occurs when the sensor 74 signal transitionsabove 60° position; the sin of 60° is 0.866. Similarly, there is a HALLxsignal transition-inducing phase change when the sensor 74 transitionsfrom the 179° position to the 180° position. Therefore, the next HALLxsignal transition-inducing phase change occurs when the sensor 74 signaldrops below 240°. The sin of 240° is −0.866.

Since the signals produced by sensor 74 are all output above 0.0 Volts,MP>0.0. Therefore, the midpoint values are representative of the sensor74 signal levels when the signal transitions from 359° to 0° and from179° to 180°. The transition signal values of Equations (3) and (4) areoffset from the midpoint value.

Graphically in FIG. 10, point 426 a on waveform 402 represents the uppertransition reference signal level as the signal from sensor 74 dropsfrom peak value 406 a to valley value 408 a. Point 428 a represents thelower transition reference signal level as the signal undergoes thistransition.

The above transition reference signal levels are thus used to determinethe levels of output signal from sensor 74 as it transits from the levelabove peak value 406 a to the valley value 408 a. These signal levelsrepresent the angular position of rotor 78 as it rotates. Thedetermination of these signal levels is used by DSP 170, in turn, todetermine when the state of the HALLx signals should be changed.

In the remaining steps of FIGS. 11A-11D, it is assumed that, in step 378it was determined that the start-up, 0 RPM, position of motor rotor 78is within 30° of the peak position represented by any one of the peakvalues 406 a, 406 b or 406 c. At start up, the peak and valley valuesstored in memory 404 are identical. Therefore, the data from which themid-point and upper and lower transition signals are determined are, foreach of the three cycles of sensor 74 signal for a single 360° rotationof rotor 78. Therefore, in order for the remaining steps used todetermine rotor position immediately after start up, there is norequirement the DSP 170 be supplied with data indicating through whichof the three 360° output signal cycles sensor 74 is presently cycling.Therefore, for purposes of example, it is arbitrarily assumed thatoutput signal from sensor 74 indicates it is near the position of peaklevel 406 a.

During the cycling of the output signal from sensor 74, the DSP 170monitors the output signal to capture the actual peak value signal levelfrom the sensor of peak 406 a. This value is stored in a RAM memory 432,FIG. 13, associated with the DSP 170. In practice, the captured peakvalue is stored in table 434 a of peak values for point 406 a.Collectively, these two processes are represented by step 436. Thepurpose of the storage of this signal level is discussed below. Itshould further be appreciated that, at start-up, it may not be possibleto execute step 436.

Then, in a step 438, DSP 170 continues to test to determine if thesensor 74 output signal falls below the upper transition referencesignal level, the level of point 426 a. Once the output signal fallsbelow this level, in step 440, the DSP resets the HALLx signals toreflect the new position of rotor 78. Then, in step 442, the DSP 170continually tests the sensor 74 output signal to determine if it fallsbelow the midpoint reference signal level, the level of point 420 a.Once this event occurs, in step 444, the HALLx signals are again reset.

In step 446, DSP 170 tests the sensor 74 output signal to determine ifthe signal level falls below the lower transition reference signallevel, the level of point 428 a. Once this event occurs, in step 448,the DSP 170 again resets the HALLx signals.

After step 448, DSP 170 re-executes steps 416, 418, 422 and 424. In FIG.10, the re-execution of steps 416, 418, 422 and 424 is shown as step450. In this execution of steps 416, 418, 422 and 424, DSP 170determines the mid-point and the upper and lower transition referencesignal levels in order to determine when, as the signal output fromsensor 74 transits from valley value 408 a to peak value 406 b, thestate of the HALLx signals are reset. On FIG. 10, the new lowertransition reference signal level is represented by point 428 b, the newmid-point reference signal level is represented by point 420 b and thenew upper transition reference signal level by point 426 c. Again, itshould be understood that at least initially, these signal midpoint andupper and lower transition levels are calculated based on the peak valuesignal level data stored in memory 404.

Also, in a step 452, the DSP 170, monitors the sensor 74 output signalto determine the actual signal level of valley 408 a. This value isstored in a table 454 a of RAM 432.

Then, as the output signal from sensor 74 rises from valley 408 a topeak 406 b, the signal is tested against the new mid-point andtransition reference signal levels. Specifically, a step 458 is executedto determine when the sensor 74 output signal rises above the lowertransition reference signal level, point 428 b. Once this event occurs,in step 460, the HALLx signals are appropriately reset. Then, a step 462is executed to test when the sensor 74 output signal rises above themid-point reference signal level, point 420 b. After this event occurs,DSP 170 resets the HALLx signals as appropriate, step 464.

In a step 466, DSP 170 then tests to determine when the sensor 74 outputsignal rises above the upper transition reference signal level, abovethe level of point 426 b. Once this event occurs, DSP 170 again resetsthe HALLx signals, step 468.

The above processes are re-executed as rotor 78 completes a full 360° ofrotation. Thus, steps 416, 418, 422, 424 and 438-448 each time thesensor 74 output signal transits from a peak value 406 x to a valleyvalue 408 x. Each time the sensor 74 output signal transits from avalley value 408 x to the next peak value 406 x, steps 450 and 458-468are executed.

From the above, it should be appreciated that each time the outputsignal from sensor 74 transits through a single sine wave cycle, fromone peak through the adjacent valley to the next peak, the HALLx signalsundergo six state transitions. When the sensor 74 output signal transitsthrough the next sine wave cycle, the HALLx signals undergoes the samesix transitions. In order to properly gate FETs 82 a-82 c and 84 a-84 c,the MCC 172 only requires the data indicating in which sextant of a sinewave cycle the rotor 78 is positioned. The MCC 172 does not need to knowin which of three sine waves generated during a 360° rotation of therotor 78 the rotor is transiting. This is why only three individualHALLx conductors are required to provide a 3-bit binary HALL signalrepresentative of rotor position to the MCC 172.

The above is also why, at start-up, it is only necessary to provide theDSP 170 with sufficient sensor data to indicate in which sextant of asine wave cycle the rotor 78 is positioned. Based on these data alone,DSP 170 is able to immediately calculate the reference levels againstwhich the later received and changing output signal from sensor 74 iscompared.

Also during the rotation of rotor 78, the DSP continually executes step436 to capture and store the values of each sine wave peak 406 a, 406 band 406 c. These values are stored in tables 432 a, 432 b and 432 c,respectively, of RAM 432. Step 452 is also continually executed as longas the handpiece 30 remains actuated in order to capture and store thevalues of each sine wave valley 408 a, 408 b and 408 c. These values arestored in tables 454 a, 454 b and 454 c, respectively, of RAM 432.

The reason the sensor 74 output signal values representative of the sinewave peaks and valleys are stored is now described by reference to FIGS.14 and 15. FIG. 14 is a plot 402′ of the output signal of sensor 74 overa complete 360° rotation of rotor 78 after the handpiece has beenactuated for a period of time. Here it can be seen that there aredifferences in the peak and valley signal levels between the individualsine waves. One reason these differences may arise is that, due toheating of the motor and the inherent physical differences in the rotormagnets, the magnetic fields emitted by the individual rotors start tovary.

Alternatively, post manufacture, the position of the sensor 74 mayshift. Such shift may be due to exposure to mechanical shock if thehandpiece 30 is dropped. If sensor 74 so shifts position, it may bepositioned so that the amplitudes of the sensed magnetic fields vary.This is a second reason that, post-manufacture, the output signal fromsensor 74 shifts from the relative uniform appearance of FIG. 11 to theuneven appearance of FIG. 14. In FIG. 14 points 406 a′, 406 b′ and 406c′ represent the new peak values' points 408 a′, 408 b′ and 408 c′represent the new valley values.

Exposure of the sensor 74 to heat as a result of tool autoclaving canalso cause the output signal of the sensor 74 to vary.

To compensate for the shifting in sensor 74 output signals, DSP 170performs the further processing of FIG. 15. Specifically, in a step 470,the DSP 170 retrieves the stored peak value data in one of the tables434 a, 434 b or 434 c of memory 432. The data, in step 472 are thenprocessed to generate a new estimated to produce a virtual signal levelfor the associated sine wave peak. In one version of the invention, eachtable 434 x contains the last captured peak signal value. This value isthen employed as the peak signal in the next set of calculations todetermine the HALLx signal transition reference signal levels.

In other versions of the invention, each table field 434 x and pluralcaptured peak signal values. In step 472 simple averaging or weightedaveraging of these values are used to generate the virtual signal levelfor the peak 406 x. These virtual values for peaks 406 a, 406 b and 406c are stored in fields 476 a, 476 b, and 476 c, respectively. Theseprocess steps 470-474 are performed for each of the three sine waves,(loop back not shown).

Similarly, in a step 480, DSP 170 retrieves the stored valley value datain one of the tables 454 a, 454 b or 454 c of memory 432. The data, instep 482 are then processed to generate a new estimated to produce avirtual signal level for the associated sine wave peak. Typically thesame algorithm used to generate the virtual signal levels for each peakis used to generate the virtual signal level for each valley 408 a, 408b or 408 c. In step 484 the calculated virtual sine wave valley level isstored in a field 486 a, 486 b or 486 c of memory 432. Process steps480-484 are performed for each of the three sine waves, (loop back notshown).

Once steps 470-474 and 480-484 are performed, step 490 is executed. Instep 490, DSP 170 substitutes these calculated virtual peak and valleysignal levels for the previous levels used to determine the mid-pointand upper and lower transition signal levels. Thus, in the futureexecutions of steps 416, 418, 422, 424 and 450, these virtual signallevels are used as the input variables for Equations 2 and 3 above.Thus, once step 490 is executed, the later generated mid-point and upperand lower transition reference signal levels are based on peak andvalley signal levels that closely approximate the actual peak and valleysignal levels generated by sensor 74. This ensures that, should theoutput signal from sensor 74 vary from manufacture or vary during asingle procedure, DSP 170 continues to assert HALLx signals that areaccurately representative of rotor position.

Returning to FIG. 8C, it should be understood that, as long as thetrigger switch 46 and/or 47 remains depressed, DSP 170 asserts theACTUATE signal, the FORWARD and/or REVERSE signal, the USER_SPEED signaland the HALLx signals, step 494. The MCC 172, in turn, in step 496,continues to gate FETs 82 a-82 c and 84 a-84 c as appropriate to causethe rotor to turn in the appropriate direction at the user-selectedspeed.

Steps 494 and 496 are continually executed as long as the trigger switch46 and/or 47 remains depressed. As represented by step 497, eventuallythe surgeon releases pressure on the trigger switch 46 and/or 47 todeactivate the handpiece. Initially, when this event occurs, the magnet56 and/or 58 moves to a position beyond which the sensor 68 or 72 cannotdetect the presence of an appreciable magnet field. Sensor 68 or 70 thusproduces an output signal that causes the DSP 170 to assert a zero speedUSER_SPEED signal, step 498.

At the time the MCC speed controller 276 receives this zero speedUSER_SPEED signal, the motor rotor 78 is turning. Therefore, the speedcontroller 276 causes the MCC to negate the assertion of signals to FETs82 a-82 c and 84 a-84 c that cause currents to be applied to thewindings 86 a-86 c that cause rotor rotation, step 502. Instead, thespeed controller asserts the BRAKE_ENABLE signal. This causes MCC 172 togate FETs 82 a-82 c and 84 a-84 c so that the windings enter a brakingmode that slows the rotation of rotor 78, step 504.

As the magnet 56 or 58 moves further away from control module 40, thefield generated is no longer sensed by sensor 66 or 70. Consequently, instep 506, the output signal from sensor 66 or 70 goes to the off state.The toggling of the signal from sensor 66 or 70 to the off state causesDSP 170 to stop asserting the AWAKE signal, step 508. This causes thedeactivation of voltage regulator 176 and amplifiers. The deactivationof voltage regulator 176 results in the like deactivation of MCC 172.Collectively, the deactivation of these components, represented by step510, is the entry of the handpiece back into the energy-saving sleepmode.

In one version of the invention, as soon as the output from sensor 66 or70 returns to the off state signal, the DSP 170 immediately negates theAWAKE signal. In another version of the invention, there is a delay ofup to 5 seconds, between when sensor 66 or 70 asserts the off-statesignal and when the DSP negates the AWAKE signal. During this delayperiod, MCC 172 continues to assert the signals that foster braking ofthe motor rotor 172. An advantage of continuing this braking is that itreduces the mechanical shock to which the individual holding thehandpiece 30 is otherwise exposed.

Handpiece 30 remains in the sleep state until, in a re-execution of step364, a trigger switch 46 or 47 is again depressed.

II. Integrated System

As discussed above tool 30 is custom configurable for each use. In step360, the trigger switch functions (forward, reverse, oscillate or off)are loaded into DSP 170. In step 362, DSP 170 is loaded with the rangeof the USER_SPEED signals it should generate as a function of thedepression of a trigger switch 46 or 47. The mechanics by which theseand other instructions are loaded into the tool 30 is now explained byinitial reference to FIGS. 16 and 17. The tool 30, in addition to thecontrol module 40 components internal to the module, also includes oneor more data transceiver heads 530 (one shown). Each transceiver head530 exchanges signals with a unit physically separate from the tool 30.As illustrated in the block diagram version of the tool of FIG. 16, thatthe transceiver head 530 will be external from the control module 40. Insome versions of the invention, it may be possible to place atransceiver head 530 internal to the control module 40. In one versionof the invention, the DSP 170 (tool control processor) exchanges signalswith the transceiver head over a serial data communications line 531.

The actual means by which the transceiver head 530 exchanges signalswith the separate unit is not, in this invention, limited to aparticular technology. In some versions of the invention, in order tofacilitate signal exchange the tool is seated in a docking station 532.Docking station 532 has its own transceiver head 534. When the tool 30 ais seated in the docking station 532, the two transceiver heads 530 and534 are positioned close enough together to allow the signal exchangetherebetween.

In some of these versions of the invention, transceiver heads 530 and534 are exposed electrical contacts that mate when the tool (tool 30 ain FIG. 17) is docked. Alternatively, the transceiver heads 530 and 534are complementary coils that allow inductive signal transfer.Transceiver heads 530 and 534 may be complementary pairs of lightemitting and light detecting components. These versions of the inventionemit and or detect light at a particular frequency including possiblylight in the infra-red spectrum. Alternatively, transceiver heads 530and 534 are complementary RF antennae. In these versions of theinvention each transceiver head 530 and 534 also includes theappropriate signal modulating and demodulating sub-circuits to convertthe exchanged signals between electrical and RF states. Transceiverheads 530 and 534 may even be complementary exposed sets of conductors.This arrangement requires physical connection of the surgical tool 30 ato the docking station. An advantage of this arrangement is that itallows for very high baud rate between the tool 30 a and the othercomponents of the system.

As seen by tool 30 b and wireless transceiver head 536 of FIG. 17, thereis no requirement a tool be in a static dock in order to for the datatransceiver 530 to exchange signals with the separate unit. In theseversions of the invention, tool transceiver head 530 and wirelesstransceiver head 536 exchange signals wirelessly even when tool 30 b isa distance of a meter or more away from head 536 and is being moved.This signal exchange by the exchange of light including infra-redpulses, radio waves, including such technologies as WiFi, Bluetooth orG3, or electromagnetic pulses.

In some versions of this embodiment of the invention, tool transceiverhead 530 and wireless transceiver head 536 are part of a surgicalnavigation system. Briefly, a surgical navigation system includes afixed unit and a mobile unit attached to the device the position ofwhich is being tracked. One of the units transmits a set of two or moresignals, typically light, electromagnetic or RF. The second unit has twoor more sensors that receive the transmitted signals. Based on thedifferences in signal strength of the received signals, a surgicalnavigation console (data processor) 540 generates data indicating theposition and orientation of the mobile unit relative to the fixed unit.Many surgical navigation systems are designed so that the mobile unitemits the light. This mobile unit, referred to as a tracker 539, isattached to the mobile device, the surgical tool 30 b of FIG. 16. Thefixed unit, referred to as a localizer 538 contains the sensors thatmonitor the emitted light. Tracker 539 contains the sensors. By trackingthe position and orientation of the tool 30 b, the surgical navigationconsole 540 generates that indicates the position of the surgical tool30 b and/or the complementary attachment relative to the surgical siteon the patient.

In some versions of the invention, tool transceiver head 530 is builtinto the tracker 539; wireless transceiver head 536 is built into thelocalizer 538.

Tool 30 a or 30 b exchanges signals with one or more units. One of theseunits is, for example, the surgical navigation console 540. A secondtype of unit with which tool 30 a or 30 b may exchange signals is ahandpiece control console 542. Console 542 is normally employed to applyenergization signals a corded surgical tool. Two such consoles 542 aredisclosed in the Applicant's Assignee's U.S. Pat. No. 6,017,354,INTEGRATED SYSTEM FOR POWERED SURGICAL TOOLS, issued 25 Jan. 2001 andits U.S. patent application Ser. No. 10/955,381 filed 30 Sep. 2004,INTEGRATED SYSTEM FOR CONTROLLING PLURAL SURGICAL TOOLS, U.S. PatentPub. No. 2006/0074405 A1, now U.S. Pat. No. 7,422,582, both of which areincorporated herein by reference.

A personal computer 544 may also serve as the unit with which tool 30 aor 30 b communicates. It should be appreciated that computer 544, or anyother of the units may serve as a gateway through which data areexchanged between the tool 30 a and 30 b and unit that is not evenlocated in the operating room/surgical suite in which the procedure isbeing performed. Such unit may, for example be a memory store device inwhich logs of data regarding the use of the tool 30 a or 30 b or thesurgical procedure are maintained. Personal computer 544 or otheroperating room unit may be connected to this remote unit through aconvention network such as Ethernet or POTS.

A voice/wireless head 546 may also serve as the unit with which tool 30a or 30 b exchanges signals. One such head 546 is sold by theApplicant's Assignee under the trademark SIDNE. Surgical personnel usinga headset-mounted microphone (not illustrated) speak commands.Voice/wireless head 546 contains speech recognition circuits thatconvert the audible commands into digital signal packets. Head 546 alsoserves as the head through which signals from a wired or wirelessdevice, wireless pendant 548 illustrated, are received. Thus, a surgeonenters a command by pressing touch screen buttons presented on pendant548. These commands are broadcast to head 546. Head 546, in turn,converts these commands into digital signal packets.

It should likewise be understood that the other remote units used tocommunicate with the tool such as the surgical navigation console 540,handpiece control console 542 or personal computer 544 may have touchscreen displays in which buttons are presented that allow commands to beentered to the tool. Alternatively, units like the surgical navigationconsole 540 or personal computer 544 have keyboards and/or mice throughwhich commands are entered.

In FIG. 17, docking station 530, wireless transceiver head 536,navigation console 540, handpiece control console 542, personal computer544 and voice wireless head 546 are tied to a common bus 552. The busmay be any bus such as an IEEE-1394 Firewire bus or LAN. Thus, in thisconstruction of the invention, each external unit navigation console540, handpiece control console 542, personal computer 544 and voicewireless head 546 can exchange signals with either one of the tools 30 aor 30 b. Also, as discussed below, this configuration of the systemfurther allows tool 30 a to communicate with tool 30 b.

Alternatively, in a less complex system, a single external unit issimply the only component connected to a docking station 530 or wirelesstransceiver head 536.

Still another means by which signal may be exchanged with a tool 30 c ofthis invention is illustrated with respect to FIG. 18. As discussedabove, some surgeons, in some circumstances, do not object to workingwith corded tools. One advantage these tools offer is that, since thepower is always available from the hospital supply network thepossibility that due to battery discharge, the tool will slow or ceaseoperation is eliminated. Thus, it is known to provide these surgeonswith a corded power pack 558. Power pack 558 couples to the tool housing32 at the location at which the cordless battery pack is normallyfitted. A cord 560 extends from the pack 558. The proximal end of cord560 plugs into a socket (not identified) part of handpiece controlconsole 542 into which the power cord for a corded tool is otherwiseattached. Console 542 supplies an energization signal to the pack 558through cord 560, Internal to pack 558 are components not illustratedand not relevant to this invention that convert the energization signalsupplied by handpiece control console 542 into a form that emulates theform otherwise supplied by battery 42.

Also internal to pack 558 and cord 560 are data conductors representedby a single line 562. The data conductors are conductive paths betweenthe data transceiver head 530 in the tool 30 c and the processor in thehandpiece control console 542. Thus, in this configuration of theinvention, tool 30 c and handpiece control console 542 exchange signalswithout use of a docking station or wireless transceiver head.

In FIG. 18 a footswitch unit 563 is shown connected to the handpiececontrol console 542 by a cable 543. Commands may be entered into thesystem of this invention by selective depression of the footswitch pedal(pedals not identified). In some versions of the system of thisinvention footswitch unit 563 is wirelessly connected to the othersystem components.

Once a communications link is established between a surgical tool 30 anda remote unit, the control processor internal to the tool (DSP 170 ofFIG. 16) transmits a number of different types of data to the remoteunit. If the data transceiver head 530 is part of a surgical navigationsystem, built into tracker 539, these data include information thatallows the surgical navigation system to determine the position andorientation of the tool. It should be recognized that these data aretransmitted when other flexible communications links are established.These communication links are other wireless links or links establishedby flexible cables such as cable 543.

DSP 170 also provides the remote unit with data indicating the operatingspeed of tool motor 34. In some versions of the invention, the PWMmeasure of motor speed generated by MCC 172 is supplied to the DSP 170.The DSP 170, based on this signal produces a multi-bit digital signalrepresentative of motor speed based on this measure of motor speed. Inalternative versions of the invention, DSP 170, based on either theperiodicity of either the output signal from sensor 74 or the HALLxsignals, calculates its own measure of motor speed. This is the motorspeed signal supplied through the data transceiver head 530 to theremote unit.

In other surgical tools of this invention wherein a device other than amotor is the power generating unit, the control processor stilltransmits a measure of power emitted by the generating unit to theremote unit. For example, if the tool is an RF ablation probe, thedistal end of the surgical attachment has a temperature sensitivetransducer, often a thermocouple. The control processor generates adigital representation of the temperature measured by the thermocoupleand supplies these data to the remote unit.

In versions of the invention wherein the surgical attachment 41 isremovable and replaceable, tool 30 also provides data regarding theidentity of the tool. In these versions of the invention, the surgicalattachment has an identification component 568 in which data regardingthe characteristics of the attachment are stored. Component 568 istypically read through an electrical or optical process. Often component568 is the form of an RFID or a NOVRAM. Tool 30 has a reader 570 capableof reading the stored in identification component 568. For example, theApplicant's U.S. patent application Ser. No. 10/214,937, SURGICAL TOOLSYSTEMS WITH COMPONENTS THAT PERFORM INDUCTIVE DATA TRANSFER, filed 8Aug. 2002, U.S. Pat. Pub. No. 2003/0093103, and incorporated herein byreference discloses how data are read from an RFID chip in a surgicalattachment, sometimes called a cutting accessory, by both corded andcordless surgical tools.

Once these data are read, the control processor forwards the data to theremote unit by the data transfer head 530.

The above-identified, incorporated-by-reference Application Ser. No.10/214,937 also discloses how data from intermediate devices between thetool housing and the actual applied-to-the-surgical site attachment areread. This document also discloses how data describing implants fittedinto place by the tool are read back to the tool. Thus, it shouldlikewise be understood that these data are likewise transmitted outthrough the data transceiver head 530 to the remote unit.

The tool control processor (DSP 170) also provides the remote unit withdata describing the operating state of the tool components. For example,as discussed above these data, for example, include data indicating thecharge level of the battery. Returning to FIG. 6B, it is appreciatedthat a signal representative of the voltage out of the battery issupplied to the DSP 170 from the junction of resistors 258 and 260. DSP170, based on the level of this signal, outputs through transceiver head530 data indicating the charge level across the battery.

A second tool operating parameter output is tool temperature. In FIG.16, tool 30 is shown as having a temperature transducer 572. Transducer572 is often placed near the heat generating component of the tool,typically the power generating component (motor 34). Alternatively,transducer 572 is positioned adjacent a surface of the tool normallygrasped by the surgeon, for example, handle 38. The output signalproduced by transducer 572 is supplied to the control processor (DSP170). The control processor generates a digitized representation of thistemperature and outputs these data by transceiver head 530 to the remoteunit.

Tool 30 has an accelerometer 574 and a noise detector 576. Accelerometer574 generates an output signal as a function of the vibration of thetool. Noise detector 576 generates a variable signal as a function ofthe noise emitted by the tool 30 and associated surgical attachment 41.The output signals from accelerometer 574 and noise detector 576 aresupplied to the control processor (DSP 170). Digital representations ofboth these tool vibration and emitted noise are transmitted through datatransceiver head 530 to the remote unit.

As mentioned above, when the power regulator (MCC 172) determines thepower generating unit (motor 34) has attempted to draw excess current, apulse bit indicating this event occurred is forwarded to the controlprocessor (DSP 170). The control processor, in turn, forwards thisinformation through the transceiver head 530 to the remote unit.

Some of the batteries 42 used to energize cordless versions of tool 30have internal temperature sensors (not shown). The signal from thistransducer is also supplied to the control processor (DSP 170). Thecontrol processor similar forwards a digital signal representative ofthe sensed battery temperature through transceiver head 530 to theremote unit.

Tool coupling assembly 39 may also have a sensor (not illustrated) thatmonitors the state of the assembly. Typically, this type of sensorasserts a first signal indicating when the coupling assembly 39 is inthe locked state; the assembly is holding a surgical attachment 41 inplace. The sensor asserts a second signal when the coupling assembly 39is in the load state; an attachment 41 can be removed from and replacedback to the coupling assembly. The output signals asserted by thissensor are forwarded to the control processor (DSP 170). Whenever thesignal from this sensor toggles, the DSP 170 transmits a data packetthrough the data transceiver head 530 to the remote unit.

III. Custom Tool Configuration

The types of data the remote unit supplies to the tool 30 are firstdescribed by reference to FIG. 19. This Figure represents the processsteps by which surgeon preferences for configuring the tool are loaded.Initially, the remote unit, for example handpiece console 542 orpersonal computer 544, is placed in an operating state in which the unitaccepts the surgeon-selected custom configuration data, (step notshown). In a step 580, the remote unit generates a touch screen displayin which the surgical personnel are invited to specify a function for ahandpiece trigger 46: forward; reverse; oscillate; or off. In step 582,the personnel enter the selected function by depressing the appropriatetouch screen button.

In a step 584, the remote unit presents one or more displays in whichthe surgical personnel are invited to specify the range at which thepower generating unit should operate based on the range of movement ofthe trigger from the partially retracted to the fully retracted states.If the power generating unit consists of motor 34, in step 584, theremote unit presents displays inviting the surgical personnel to enterthe selected minimum and maximum speeds at which the motor shouldoperate based on the extent to which the trigger 46 or 47 is retracted.As discussed below, in step 584, the remote unit also invites thesurgical personnel to indicate the rate of change of the powergenerating unit, for example, stepped speed increases or linearincreases. In step 586, by depressing the appropriate buttons presentedon the remote unit display, the surgical personnel enter the operatingrange profile wanted by the surgeon.

Steps 580-586 are then re-executed for the second trigger switch 47,(loop back not shown). Once the surgeon-selected operating configurationsteps 360 and 362 are executed. Steps 360 and 362 are executed by theremote unit forwarding the surgeon-selected operating configuring datato the docking station transceiver head 534, the wireless transceiverhead 536 or over cable 562 depending on which tool 30 a, 30 b or 30 c isto be configured. These data are then loaded into the appropriatelocations in RAM memory 432 of the control module 40 (memory locationsnot shown). Then, depending on which trigger 46 or 47 is actuated andthe extent to which the trigger is actuated, the power generating unit(motor 34) is actuated in accordance with the surgeon's preferences.

Tool configuration may be set as a function of the specific surgicalattachment 41 coupled to the tool. In FIG. 20, the initial step 590 ofthis process is the detection by the system that a new surgicalattachment has been coupled to the tool 30. There are a number of meansby which the specific identity of the attachment is determined. Inversions of the invention in which the attachment 41 has an attachmentidentification component 568 and tool 30 has a complementary reader 570,the reader performs this function.

In alternative configurations of this invention, another componentperforms the function of reading the data stored in the attachmentidentification component. For example, Applicant's U.S. PatentApplication No. 60/634,588, filed 9 Dec. 2004, entitled Wireless SystemFor Providing Instrument And Implant Data To A Surgical Navigation Unit,U.S. Patent Pub. No. 2006/0142656 A1, incorporated herein by referencediscloses how an intermediate attachment reads data from the actualattachment applied to a surgical site or to an implant the tool is usedto fit to the surgical site. These data are then transmitted to a statichead such as navigation localizer 538.

In still another version of the invention, the attachment data areentered manually. In these versions of the invention, control processor(DSP 170) transmits a signal to the remote unit when the signal assertedfrom the sensor integral with the coupling assembly 41 transitions fromthe from the load state to the run state. The remote unit, for examplethe handpiece control console 542 or personal computer 544, interpretsthis information as an indication that a new surgical attachment 41 isattached to tool 30. Once the remote unit determines that this event hasoccurred, the remote unit generates a display requesting the surgicalpersonnel identify the newly-attached surgical accessory 41, (steps notshown).

Once step 590 is executed, a step 592 is performed in which thehandpiece operating parameters for the newly attached attachment areidentified. Step 592 is performed by the reading of additional datastored in the attachment identification component 568. Alternatively,step 592 is performed by retrieving data in a remote lookup that, foreach type of surgical attachment 41, identifies certain operatingcharacteristics. This look-up table may be in the operating room remoteunit employed to configure the tool 30 or in a file server off-site fromthe operating room. This operating parameter data is a function of thetype of tool and attachment. For example, if motor 34 comprises thepower generating unit and the surgical attachment is a bur, these datamay be an initial and maximum speed for the bur. If the tool is an RFablation device, and the surgical attachment is an ablation electrode,these data are the preferred and maximum temperatures at which theelectrode should operate and the maximum current the electrode shoulddraw.

It should be appreciated that step 592 may be performed by the manualentry of data through the remote unit.

In a step 594 these operating characteristics are displayed by theremote unit employed to configure the handpiece 30. As part of thisdisplay, and shown as a step 596, the surgical personnel are invited toaccept or reset the operating characteristics of the tool based on theretrieved operating characteristics. Step 598 represents the resettingof the tools operating characteristics by the surgical personnel awayfrom the retrieved characteristics. Thus, step 598 is an execution ofstep 586 in which buttons are depressed to reset the operatingcharacteristics of the tool up or down from the retrievedcharacteristics.

Once, in step 596, the preferred operating characteristics are acceptedor, in step 598, the characteristics are reset, a step 600 is executed.Step 598, similar to step 362, is performed in which the attachmentspecific parameters are loaded into the control processor (DSP 170).

From the above description, it is clear that the surgeon has the optionof configuring the tool 30 to operate in a state greater than thatspecified by operating characteristic data specified for the attachment41. The system of this invention provides additional feedback regardingwhen tool 41 is so operated. Specifically, as represented step 602,there is monitoring of when the operating state of the tool exceeds adefined state established from the retrieved operating characteristics.For example, in step 602 operation of motor 34 is monitored to determineif the motor operating speed exceeds a level based on the preferredmaximum speed. This rate is, for example, between 1.0 and 2.0 times thepreferred maximum operating speed.

The monitoring of step 602 may be performed by the tool controlprocessor (DSP 170) or the remote unit, (handpiece console 542 orpersonal computer 544). If the monitoring is performed by the remoteunit, in a separate step (not illustrated) the tool control processorsends a message to the remote unit indicating that the operating stateis being exceeded.

Once it is determined that the operating state is being exceeded, thesystem executes steps 606 and 608. In step 606, the remote unittemporarily prevents the tool 30 from being operated beyond the definedoperating state. For example, if the tool contains a motor 34, thecontrol processor (DSP 170) does not assert signals that allow the powerregulator to drive the motor above the defined speed level. If the toolis an ablation tool, the control processor does not assert signals thatallow the power regulator to apply current above the defined level to beapplied to the ablation electrode.

In step 608, the remote unit generates a display advising the surgeonthat it appears the tool is going to be driven beyond the defined level.Surgical personnel in step 610 then must acknowledge it is the intent toso operate the tool. Once the surgical personnel enter thisacknowledgment, the remote unit releases the lock on the tool operation,step 612. In step 612, the remote unit performs this function by sendingan appropriate command to the tool control processor through transceiverheads 536 and 530 (or conductor 562). The tool control processor, instep 614, then releases the operating lock on the tool.

In some versions of this invention, once the acknowledgement of step 612is entered, the system records in the event logs for the tool and thesurgical procedure that the tool 30 and attachment were operated at arate above the preferred maximum operating rate.

As represented by the process steps of FIG. 21, the remote unit alsoregulates the operation of tool 30 based on the monitored operatingcharacteristics of the internal components of the tool. As discussedabove, the tool control processor (DSP 170) forwards data packets to theremote unit containing information regarding the operating condition ofthe components internal to the tool. In some versions of the invention,these packets contain data that quantifies the operating state orcondition. This type of data packet, for example, contains an exactindication of the temperature of the tool motor 34 measured bytransducer 572. Alternatively, based on temperature monitoring performedby the tool control processor (DSP 170), the control processor sends adata packet whenever the output signal from transducer 572 rises above adefined level.

Similar monitoring and data packet generation is performed based theoperating characteristic data received by monitoring the charge acrossthe battery 42, the signals received from accelerometer 574, the noisedetector 576 or the temperature transducer internal to the battery. Datapackets may also be sent by the control processor when the controlprocessor receives an indication that the motor is drawing an excessamount of current.

In FIG. 21, step 620 represents the detection that the tool 30 is nolonger in the normal state and has entered an exceptional operatingstate. Examples of exceptional operating states include: a determinationthat the battery will soon be discharged; the battery, as indicated by arise in its temperature; is approaching a breakdown condition; the tool30 is at or approaching a temperature in which it will be difficult tohold; that the tool is vibrating excessively or developing excessivenoise; or that the motor has been excessively heated. Still anotherexception operating state occurs when the power generating unit (motor34) repeatedly draws current above the set limit level at frequencyabove a pre-defined level.

As mentioned, the determination of step 620 may be made by themonitoring performed by the tool control processor (DSP 170).Alternatively, the remote unit, the handpiece control console 542 orpersonal computer 544, may perform the monitoring of step 620 based ondata transmitted by the tool control processor.

If, in step 620, it is determined that the tool is in an exceptionaloperating state, the remote unit, in step 622, presents a warningregarding the operation of the tool. This warning indicates the natureof the exception. For example, if in step 620 it is determined that thebattery 42 is almost completely discharged, this information ispresented. If, in step 620, it is determined the motor temperature isrising to a level at which it may cause motor malfunction or damage,this information is presented.

Either simultaneously with or immediately after step 622, the remoteunit presents the surgeon with a conservative operation mode option,step 624. In this step, the surgeon is given the option of operating thetool at a reduced operation level in order to prevent operation of thetool from decaying or being interrupted. Typically this conservativeoperation mode limits the rate at which the power generating unitoperates. For example, if the power generating unit is motor 34 and instep 620 it is determined that the battery is close to completedischarge or motor temperature is approaching an unacceptable level, theconservative operation is the reduction in the maximum speed at whichthe motor can be operated. Another example of the conservative operationmode is the reduction in the power an RF ablation probe can apply to thesurgical site.

In step 626 the surgeon accepts or declines the invitation to operate inthe conservative mode. A surgeon may select to decline operation of thetool in the conservative mode if it is known that tool use required foronly a short time period. If the surgeon declines to accept conservativeoperation of the tool, operation continues as before, step 627. Itshould be appreciated that as part of this step, the remote unit writesdata into the external tool log that the tool entered a particularexceptional state and the surgical personnel declined the invitation tohave the tool placed in the conservative operation mode.

Alternatively, given that the surgeon may need the tool for extendedtime and the procedure is at point wherein interruption of tooloperation is undesirable, in step 626 he/she accepts the conservativeoperation mode.

If the conservative operation mode is accepted, in step 628 the remoteunit loads the conservative operating mode parameters into the tool.Step 628 is thus analogous to a re-execution of step 362 in which newoperating characteristics are loaded into the tool control processor(DSP 170). Once step 628 is executed, the tool continues to operatethough at the levels specified by the conservative operation modecharacteristics.

This feature of the system of this invention provides a means tocontinue to operate the surgical tool 30 in the event the occurrence ofan exceptional event may otherwise make it difficult to continue tooperate the tool.

Surgical tool 30 of this invention, in combination with the surgicalnavigation system, is further configured to provide the surgeon withnotice when the surgical attachment is approaching or at body locationat which the attachment should not be applied. As represented by step632 of FIG. 22, during the surgical procedure, surgical navigationconsole 540 monitors the position of the surgical accessory 41. Thismonitoring is performed based on the tracker 539 attached to the tool30, to the accessory or to the intermediate accessory between the tooland the accessory actually applied to the site.

Prior to the initiation of the procedure, the surgical navigationprocessor 540 is provided with map data that indicates the bodylocations adjacent the surgical site to which the surgical attachmentshould not be applied or should only be applied with extreme care.Collectively, these areas are referred to as “no cut zones”. (Step notshown)

In step 634, based on the accessory position data acquired in step 632,surgical navigation processor 540 determines if the attachment 41 is ator has crossed the boundary of a not cut zone.

If the surgical attachment 41 is so positioned, the surgical navigationconsole 540, in step 636, loads a low speed or zero speed instructioninto control processor (DSP 170) of tool. Step 636 is thus are-execution of step 362. In step 636, the tool control processor (DSP170) is loaded with data indicating that the tool is to either bedeactivated or, at a minimum, run at very low operating rate. Forexample if the power generating unit is motor 34, the control processoris loaded with instructions indicating the motor is to be run at eithera low speed, (motor maximum speed is appreciably lowered) or totallydeactivated. If the power generating tool is an RF ablation probe, theinstructions loaded in step 636 are typically instructions that the toolshould be deactivated. Based on these instructions, the controlprocessor generates the appropriate USER_SPEED signals to the powerregulator (MCC 172). The power regulator, in turn, appropriately resetsthe operation of the tool power generating unit. (Steps not shown).

The execution of step 636 by the surgical navigation unit 540 and thesubsequent reduction in operation of the tool 30 are performed toimmediately minimize, if not prevent, the extent to which attachment 41is active in the no cut zone.

Essentially simultaneously with the execution of step 636, in a step638, a warning is presented. Typically this warning is presented of thedisplay integral with the surgical navigation processor 540. In step 638this warning contains in indication that use of the tool has beenreduced or totally blocked because the attachment 41 is at or hasentered the no cut zone.

Integral with the warning, also in step 638, the surgeon is alsopresented with an override option. The override option allows thesurgeon to continue to operate the tool even though the attachment 41 isnear or has crossed into the no cut zone. Step 640 depicts the processin which the surgeon selectively accepts the override option. If thisoption is not selected, operation of the tool continues based on thecommands entered in step 636.

Alternatively, in step 640, the surgeon enters the override command. Ifthis event occurs, in step 642, a remote unit, the surgical navigationcontroller processor 540, the handpiece control console 542 or thepersonal computer 544, loads override operating characteristics in thetool control processor (DSP 170). These characteristics, which arepredefined, limit the use of the surgical attachment at or near the nocut zone. For example, if in step 636 use of the tool is totallyblocked, in step 640, the override characteristics may allow operationof the tool to continue however at a lower operating rate.

Alternatively, the instructions loaded in step 636 may have only causedthe control processor to reduce the rate at which the tool powergenerating unit operates. In this event the instructions loaded in step642 direct the control processor to allow the power generating unit tooperate at a higher rate than that specified in the instructions of step636. In step 642, the new instructions may even direct the controlprocessor to allow the power generating unit to continue to be operatedat the defined rate before step 636 was executed.

IV. Kinematic Machine Positioning

The integrated system of this invention is used to precisely position akinematic machine that is fitted to a patient. Typically, a kinematicmachine has at least one and often two or more moveable links that areselectively positioned relative to a static point on the body of thepatient. By precisely locating the links, a therapeutic task isaccomplished using the machine. FIG. 23 illustrates one such kinematicmachine, a jig assembly 648. Jig assembly 648 includes a fixed markerblock 656 and a jig head 650 that is moveable relative to the mountingblock. Jig head 650 is formed with a guide slot 652. During the processof attaching an implant to a bone 654, jig head 650 is preciselypositioned. Once the jig head 650 and guide slot 652 are so positioned,a saw blade is inserted in the guide slot 652 to remove a section of thebone in order to create a space in which the implant is fitted.

The marker block 656 is mounted to the bone 654. The jig head 650 ismoveably attached to a positioning block 658 that itself is moveablyattached to the marking block 656. The integrated system of thisinvention is used to precisely position jig head 650 to ensure thetissue is cut at the appropriate location.

As represented by step 672 of FIG. 24A, the integrated process of thisinvention starts with the mounting of the marker block 656 to a fixedlocation. Typically, this location is a position on the body, forexample, to a section of bone 654. Usually, the surgical navigationsystem is employed to facilitate the positioning of the marker block ata location close to where the surgical component, here the jig head 650is to be located. In one version of the invention, pins 674 integralwith the marker block 656 are used to hold the marker block to the bone654.

In a step 676, the jig head 650 or other surgical device or surgicalimplant is fitted to the marker block 656. In one version of theinvention the jig head 650 and marker block are provided withcomplementary feet and grooves (not illustrated). The feet of one of thejig head 650 or marker block 656 are dimensioned for a close sliding fitin one or more grooves formed in the other of the marker block 656 orjig head 650. Other means may be provided to facilitate the closesliding fit of these two components.

In the illustrated version of the invention, jig head 650 is moveablyattached to the positioning block 658 and the positioning block 658 ismoveably attached to the marker block 656.

In addition to a coupling assembly that allows jig head 650 to moverelative to marker block 656, these two components are collectivelyprovided with a complementary drive assembly. This drive assembly allowsjig head 650 to move relative to the marker block 656. In the disclosedversions of the invention, there are two drive assemblies. A first driveassembly vertically moves positioning block 658 relative to marker block656. In FIG. 23, this drive assembly is represented by a circular gear680 rotatingly mounted to the marker block 656 and a worm gear 682rotating to the positioning block 658. A second drive assembly moveshorizontally moves jig head 650 relative to the positioning block 658.This drive assembly is represented by a circular gear 684 rotatinglymounted to the positioning block 658 and a worm gear 686 rotatinglyfitted to jig head 650.

Once the jig assembly 648 is fitted to the patient, in step 690 thesurgical navigation unit determines the original location of the jighead. In FIG. 23 jig head 650 is shown as having three LEDs 692. TheLEDs 692 represent a tracker built into the jig head 650. Positioningblock 658 is also shown as having three LEDs 693. LEDs 693 facilitatethe determining of the position of the positioning block 693 with thesurgical navigation unit.

In a step 694 an initial displacement rate for the jig head 650 isgenerated. This displacement rate may be generated by one of the remoteunits such as the surgical navigation console 540, the handpiece controlconsole 542 or personal computer 544. The displacement rate is based onthe previously set position on the patient at which the jig head 650should be positioned and the current position of the jig head 650obtained in step 690. Generally, the initial displacement rate isinversely related to original distance of the jig head (or implant)relative to the previously determined final location. Also in step 694an initial speed for the handpiece motor, based on the initial jig headdisplacement rate is determined. In a step 695, the initial handpiecemotor speed is loaded into the handpiece control processor (DSP 170). Amessage is also displayed indicating that these tasks were executed.

In a step 696, the surgical tool 30 is attached to the drive assembly.In FIG. 23, this is represented by the coupling of surgical tool 30 tothe worm gear 686 of jig head 650. This coupling is accomplished byproviding the drive assembly and the moving member of the surgical toolwith complementary coupling features. For example, the proximal ends ofworm gears 682 and 686 are provided with closed end square shaped bores.The drive shaft of the surgical tool 30 has a distal end square shapethat allows the shaft to closely slip fit into the proximal end bores ofthe worm gears 682.

Once step 696 is executed, in step 698, the surgeon actuates thesurgical tool 30 so as to position jig head 650. In the versions of theinvention in which, in step 694 jig head displacement rate/motor speedare calculated and loaded, upon the depression of the trigger switch 46or 47 to actuate the tool, the control processor (DSP 170) automaticallysets the USER_SPEED so that motor 34 runs at the specified speed. Themechanical energy output by the surgical tool is employed by the driveassembly to move the jig head 650 to the appropriate final position,(step not shown).

Throughout the time in which jig head 650 is displaced, the surgicalnavigation system monitors the position of the jig head, step 702. In astep 704, the surgical navigation console 540 or the handpiece controlconsole 542, based on the changes in distance between the jig head andthe target position, updates the jig head displacement rate/motor speed.As part of step 704, command data setting the new user speed arecontinually transmitted to the handpiece control processor (DSP 170).Based on these data, the control processor continually resets theUSER_SPEED signal. Thus, as the jig head 650 approaches the targetposition, the speed at which it moves decreases.

Eventually, the surgical navigation processor 540, in step 706determines the jig head reaches the target position. In FIG. 24B, thisis represented by the loop backed repetitive execution of steps 702, 704and 706. Once the event occurs, the surgical navigation processor 540 orhandpiece control console 542 sends a deactivation command to thesurgical tool, step 708. Upon receipt of this command, control processor(DSP 170) sets the USER_SPEED signal to zero. This causes powerregulator (MCC 172) to deactivate and brake the motor rotor 78.

A step 710 is then executed to clamp the jig head 650 in the desiredposition. In FIG. 23, a set screw 712 is shown as extending throughmarker block 656. Set screw 712 is positioned to bear againstpositioning block 658. The set screw 712 thus functions as the clampingmember that holds positioning block 658 in the correct position. Asimilar set screw, not illustrated, can be used to hold jig head 650 inposition.

This configuration of the integrated tool system of this invention usesthe motorized surgical tool 30 to precisely position a surgicalcomponent or implant. Once the kinematic machine is so positioned, thetool 30 is deactivated.

Other kinematic machines the system and method of this invention can beused to position include body fixator units. One such type of anassembly is halo type unit used to hold the skull static relative to thecollar bone. Other kinematic machines are used to hold spinal disks infixed positions relative to each other. Still other kinematic machineshold fractured bone fragments together. It should likewise beappreciated that the method of FIGS. 24A and 24B is not limited to thepositioning of kinematic machines. The system and method of thisinvention may also be used to precisely position in an implant relativeto body tissue markers.

V. Integrated Cement Mixing

A system with surgical tool 30 of this invention is also used to mixsurgical cement as seen by reference to FIG. 25. Here, the cement powder740 is contained in a cartridge 742. A monomer (not illustrated) is alsoplaced in the cartridge 742. A blade 744 in the cartridge mixes thecement powder and monomer together to form an uncured mass of cement. Ashaft 746 attached to the blade 744 extends out of cap 748 disposed overthe cartridge. 30. Surgical tool 30 is actuated at a select speed for aselect Shaft 746 is coupled to an output shaft 750 of the surgical toolamount of time to so that, at the end of the mixing process the cementmass hardens, sets, at the desired rate and when hardened, has thesurgeon-selected desired porosity and opacity.

FIGS. 26A, 26B and 26C collectively form a flow chart of the processsteps executed by the system of this invention to facilitate the propermixing of the cement. The process starts with, in steps 750 and 752,respectively, the entry of the type of and quantity of cement to bemixed. There are number of means by which steps 750 and 752 areexecuted. In one version of this invention, cement type and quantityinformation are entered by depressing specific touch screen buttons onone of the components of the system such as the handpiece controlconsole 542, personal computer 544 or pendant 548.

Alternatively, as represented by FIG. 27, these data may come from thepackets 754 in which the cement is held prior to mixture. Here, attachedto the packet 754 is a radio frequency identification chip (RFID) 756such as is available from Philips Semiconductor. RFID 756 is disposedover packet 754. A small piece of RF permeable protective material 758such as paper or plastic is disposed of the RFID 756 to hold the RFID inplace.

Internal to RFID 756 is a memory represented by the table 760 of FIG. 28in which data describing the characteristics of the cement are stored.These data include an indication of the cement type, represented byfield 762. Data representing cement quantity are stored in field 764. Anexpiration date for when the cement can last be used are stored in field766. Data indicating the monomers that should be mixed with the cement,or that at least are preferred for mixture with the cement, are storedin field 768. Field 768 also contains data regarding the quantity ofmonomer that should be mixed with the given packet of cement. Dataregarding monomers that should not be used to harden the cement arestored in field 770. Field 772 stores data that describes acceptableadditives that can be combined with the cement. Field 774 contains alist of additives that cannot be combined with the cement.

The RFID 756 is scanned by a reader (not illustrated) in a probe 780.Probe 780 and reader are connected to another component of the systemsuch as handpiece control console 542 or computer 544.

Alternatively, in some versions of the invention, cartridge 742 containsa premeasured quantity of the cement powder 740. In these versions ofthe invention, an RFID 782 is integrally associated with the cartridge.RFID 782 may be housed in the cartridge cap 748. In these versions ofthe invention, data may be read by the RFID reader in the surgical tool30 or the reader in the probe 780. In some variations of this version ofthe invention, RFID 782 is attached to the packaging in which thecartridge 742 is stored. Here, steps 750 and 752 are performed withprobe 780.

Once steps 750 and 752, the system, in step 786, determines if thecement 720 is appropriate for the procedure being performed. In step 786a number of separate evaluations are performed. One evaluation is todetermine based on the data in RFID expiration field 766 whether or notthe expiration date for the use of the cement has passed.

Also, based on other data, in step 786 determination is made regardingwhether or not the cement type and quantity are appropriate for theprocedure. The reference data from which these determinations are mademay come from data entered by the surgical personnel entered before theprocedure. Alternatively, these data may be obtained from anothercomponent or instrument used to perform the procedure. For example, thepreviously mentioned and incorporated-by-reference Applicant's U.S.patent application Ser. No. 10/214,937, SURGICAL TOOL SYSTEMS WITHCOMPONENTS THAT PERFORM INDUCTIVE DATA TRANSFER, filed 8 Aug. 2002.

U.S. Pat. Pub. No. 2003/0093103 describes how surgical implants areprovided with RFIDs. FIG. 29 is a partial listing of some of the datastored in a memory 790 of one of these RFIDs. As represented by field792, these data include an indication of the type of cement that can beused to attach the implant. Data indicating the cements that should notbe used are stored in field 794. A field 796 stores data indicating thequantity of cement typically required. If the implant fitted in theprocedure is of the type having the data of memory 790, then prior tostep 750, the system, for example personal computer 544 displays thepreferred cement type and quantity data.

If it is determined that the cement is unacceptable, the system displaysa warning as represented by step 797. In step 797, the warning indicatesthe cause of the warning, for example, wrong cement, out of date cementor recalled lot. Not shown are steps performed by the surgical personnelafter the warning is presented. The surgical personnel may decide to mixa new batch of cement, restart the process. Alternatively, the surgicalpersonnel may decide the cause of the warning does not warrant therestart of the mixing process, for example, if the cement expirationdate only recently passed. In such a circumstance, the surgicalpersonnel press an acknowledgement button presented with the warningdisplay. The entry of the acknowledgement is then recorded on the logfor the surgical procedure. In FIG. 26A, the steps executed after thegeneration of the warning, step 797 are not shown. Step 798 is theadding of the cement into the mixing unit, for example cartridge 742.

Once it is determined that the cement is satisfactory, the system, instep 799, displays indications of the monomers it is acceptable to mixin with the cement and the sequence in which the cement and monomershould be initially loaded in the mixing unit (cartridge 722). Thesedata may be preprogrammed into the system. Alternatively, as representedby fields 768 and 771 of memory 760, these data may be stored in andretrieved from the RFID 756 integral with the cement.

When it is time in the sequence to enter the monomer, data regarding thecharacteristics of the monomer are input into the system, step 803. Thisstep may be performed manually. Alternatively, an RFID 804 attached tothe container 805 in which the monomer is stored is read. This RFID 804is read by the same component used to read cement packet RFID 756. RFID804 includes a memory represented by table 808 of FIG. 30. Internal tothe monomer RFID memory 808 are: a data field 810 indicating monomertype; a data field 812 indicating monomer quantity; and a data field 814indicating expiration date. Not illustrated by also understood be inRFID memory 806 as well as memory 760 of cement RFID 756 are data fieldsin which information regarding manufacturer and manufacturing lot numberare stored.

Once step 803 is executed, the system performs a step 818 to determineif the monomer is acceptable. This step is performed based on previouslyobtained reference data. These reference data may be hard stored in thesystem, stored prior to the procedure or the data obtained from thecement RFID 756. If in step 818 it is determined the monomer selectedfor addition is not acceptable, the system displays a warning, step 820.Step 820 is similar to step 797 in that the surgical personnel are givena notice of the cause for the warning. The surgical personnel can thendecide to use the monomer or select a new container of monomer. If thesurgical personnel elect to use the potentially questionable monomer, anacknowledgement is entered. The steps executed after the execution ofstep 820 not shown.

If in step 818 it is determined that the monomer is acceptable, it isadded to the mixing unit (cartridge 742), step 821.

While the steps are not shown, it should be understood that the systemand method of this invention also monitor the volume of monitor added tothe cement mixture. The volumetric determination is made by assuming allthe monomer, as indicated in quantity field 812 is added to the mixture.If this volume is either too much or great for the quantity of thecement as specified in field 768, an appropriate warning message isdisplaced. If this evaluation indicates too much monomer has been addedto the system, this system thus provides has notice so a decision can bemade regarding whether or not the mixture should be discarded. If theevaluation indicates that too little monomer has been added, the noticeprovides an opportunity to add additional monomer.

After the cement and monomer are placed in the mixing unit, additivesmay also be placed in the unit as represented by step 822. One additivesometimes including in a cement mixture is therapeutic, for example anantibiotic. Another type of additive that may be included is materialdesigned to improve the ability of a medical imaging unit to capture animage of the cement. Barium sulfate is sometimes added to cement forthis purpose.

In FIG. 26A, the addition of the additives is shown as a single step822. It should be appreciated that in the system and method of thissystem, an image may be presented indicate the need to include theadditive or the process is not at a point where the additives are to beadded. Data regarding the characteristics of the additives to be addedare entered using manual or electronic means similar to how the dataregarding the cement powder and monomer are entered. RFIDs integral withthe containers in which the additives are stored are read. Once thesystem is provided with the additive-describing data, a step similar tostep 818 is performed to determine if the additive and/or quantity ofthe additive(s) are acceptable.

The reference data by which this determination is made may come fromfields 772 or 774 of the cement RFID memory 760. Alternatively, thesereference data are read from fields 823 and 824 of implant RFID memory808. Here, field 823 contains data indicating the additives that areacceptable for use or desirable/required for use with the implant. Field824 contains data describing additives that are not appropriate for usewith the implant. It should be appreciated that fields 772 and 823 alsocontain data indicating the volume or mass of additive that should beadded to ensure an effective amount is present. Similar data describingacceptable, desirable, required and unacceptable data are also stored inthe some of the RFIDs 804 associated with the monomer containers.

Step 822, it should also be understood, includes the sub step ofverifying the additive is appropriate for inclusion into the cementforming mixture and that a sufficient quantity of the additive has beenincluded.

It should also be appreciated that the above process steps may berepeated and/or re-executed in a different sequence. The exact number oftimes the above steps are re-executed and their execution sequence are afunction of the quantity of the cement to be mixed and the sequence inwhich the cement, monomer and additive are to be added to the mixingunit (cartridge 722). Some cements and monomers are mixed in alternatingorders. Other cements and made by first adding all the powder and thenall the monomers. Such sequence data (obtained from cement RFID 756) andquantity data, (obtained from implant RFID memory 790) are used by thesystem to initially determine the sequence in which the initiallycomponents adding steps are performed. It should be appreciatedinstructional data indicating the sequence for performing these stepsare presented by the system on one of the displays.

Once the materials that are mixed to form the cement mixture are addedto the mixing unit, a surgeon-selected set time is entered into thesystem as represented by step 828. “Set time” is the amount of time,post-mixing, before the uncured cement has its peak exothermic reaction.The occurrence of this event means that the cement has hardened to apoint at which it can no longer easily be molded. The “working time,”the time in which the cement can easily be molded into shape, isdirectly proportional to and less than the set time.

In step 829, data are entered into the system indicating the desiredporosity of the cured cement. These data may be entered or based on thedata in field 832 of the implant RFID memory 790. In some versions ofthe invention, step 829 starts with the display of the porosity levelretrieved from implant memory field 831. The surgeon then accepts therecommended level or adjusts the level based on the particulars of thepresent surgical procedure. In versions of the invention wherein theimplant does not provide porosity level, the system, in step 829,directs the surgeon to enter a selected porosity level.

The system, in step 831 also determines the characteristics of the toolemployed to perform the mixing. These data are entered by pressing thebuttons presented on the touch screen display. Alternatively, these dataare known by the system based on tool identifying characteristic dataprovided by the tool control processor (DSP 170) through datatransceiver head 530.

In step 832, the ambient temperature and relative humidity are enteredinto the system. These data are entered manually. Alternatively, anenvironment monitor 833 is in the operating room and connected to one ofthe other units, (handpiece control console 542 or personal computer544). Environmental monitor 833 contains transducers sensitive totemperature and humidity. The output signals generated by thesetransducers are forwarded to the system unit controlling and monitoringthe cement mixing process. In this construction of the system, step 832is performed without human participation.

In step 834 the particularities of the mixing system are entered intothe system. These particularities include: type of mixing unit (bowl orcartridge); blade type; presence of blade oscillating unit; presence ofheater.

Based on the above data, the system, in step 836, generates the mixingprocess variables. These variables include: the speed at which the motor34 should be actuated; the mix duration, the total time the motor shouldbe actuated; and the blade direction; (unidirectional or cyclicforward/reverse/forward/reverse. If the mixing system is capable oflongitudinally oscillating the blade the oscillation rate is determined.If the mixing unit has a heater, the temperature to which the mixingunit should be heated in determined.

In step 836, the above mixing variables are determined based on datastored in look-up tables contained in a component such as personnelcomputer 544. Alternatively, or in combination with the look-up tabledata, the mixing variables are determined based on execution of storedalgorithms. The data entered in steps 750, 752, 803, 822, 828, 829, 831,832 and 834 and/or from the look-up tables function as the inputvariables for the algorithms.

The look-up table and algorithm constants, coefficients and exponentsare typically determined by empirical analyses. Table 1 lists generalrelationships between the above-described variables and the rate atwhich the motor 34 should be operated and/or mix duration.

TABLE 1 General Relationships Between Input Variable For Cement Mix AndMix Speed (Motor RPM) And Mix Duration Type of Cement, i.e., Higher MixSpeed and/or Increased Cement Viscosity Longer Mix Duration IncreasedCement Quantity Higher Mix Speed and/or Longer Mix Duration Addition ofAdditives Higher Mix Speed and/or Longer Mix Duration Decreased Set TimeHigher Mix Speed and/or Longer Mix Duration Reduced Porosity Higher MixSpeed and/or Longer Mix Duration High Ambient Temperature Slower MixSpeed and/or Shorter Mix Duration High Ambient Rel. Humidity Higher MixSpeed and/or Longer Mix Duration

Motor speed and mix duration is also a function of tool type. Forexample, if the attached tool is a slow speed reamer the mix durationmay be longer than if the tool is drill that is typically run at ahigher speed. Variables such as mixing system components such as bladetype and type of mixing unit have varying effects of mix speed and/ormix duration.

Generally, if a relatively short set time for the cement is desired, thesystem determines the mixing unit heater decrease the temperature of thecompounds being mixed. The rotational direction of the blade and whetheror not it should be longitudinally oscillated are generally functions ofcement type, the type(s) of additive(s), and blade type.

Also in step 836, the viscosity of the mixed cement at the end of themixing process is determined. Again, this is generally determined byempirical process. Look-up data based on the empirical processes arestored in the system, for example personal computer 544 or in a centraldatabase in the hospital. Based on these data, a determination of thecurrent that should be drawn by the tool motor 34 is also generated instep 836. In some versions of the invention, only these latter data aregenerated. In preferred versions of the invention, the system generatesdata representative of the current the motor should draw over timeduring the actual mixing process. Plot 840 of FIG. 31 represents onesuch set of data.

In step 842, the system then forwards the mix settings to the toolcontrol processor (DSP 170). At a minimum, in step 842, the systemprovides the tool control processor with data indicating the speed atwhich the motor should be driven as determined in step 836. If the bladeto be forward/reverse/forward/reverse cycled, the minimal data alsoincludes preloading into the control processor an indication of how longthe motor should be rotate in each direction. In step 842, the systemmay further provide the tool control processor with data indicating thedetermined mix duration. Also as part of step 842 is the display by thesystem that the tool is set to mix the cement.

The next step, step 844, is the actuation of the tool to perform themixing. It should be appreciated that before the mixing, the blade shaft746 is coupled to the tool shaft 750 to affect the desired rotation ofthe blade, (step not shown). Since the tool speed has already been set,the surgical personnel do not have exert mental or physical effort toprecisely depress the trigger switch 46 or 47 to ensure the motor turnsat the right speed and/or duration. Based on the preloaded instructions,control processor (DSP 170) asserts the appropriate USER_SPEED andFORWARD and REVERSE signals to power regulator (MCC 172). Thus, thepre-loaded instructions cause the motor 34 to turn at the right speedand in the right direction (or directions).

Once the surgical tool is actuated, the system, as represented by step846, monitors both for how long the tool is actuated and the currentdrawn by the handpiece motor. In some versions of the system of theinvention, these data are transmitted to the remote unit (handpiececontrol console 542 or personal computer 544).

Steps 848 and 850 represents that, throughout the mixing process, thesystem, typically the remote unit, monitors the current drawn by thehandpiece motor 34. Specifically, in step 848, the system monitors adetermination is made regarding whether or not the current drawn issignificantly below the expected current draw at the given time duringthe mixing process. In FIG. 31, the acceptable minimal current draw isshown by dashed plot 852. Thus at time t_(N), the acceptable minimalcurrent drawn is I_(MIN). If the current drawn is below the acceptableminimal current drawn level, the cement is most likely less viscous thenit should be at that time in the mixing process. If the cement is inthis state, the system responds by executing step 856 in whichinstructions are generated to increase the time of mix duration and/ormotor RPM. (Not shown are the steps transmitting these instructions tothe tool 30 and their execution by the tool.)

In step 860, the system determines if the drawn current exceeds amaximum level for the time point in the mixing process. In FIG. 31 themaximum current draw at any time is represented by dashed plot 858. Attime t_(N) the acceptable maximum current draw is I_(MAX). If thecurrent drawn is above the acceptable maximum level, the cement mixtureis most likely more viscous than it should be at this point in time inthe mixing process. If the cement is in this state, the system, in step861, generates instructions to reduce the time of mix duration and/ormotor RPM. (Not shown are the steps transmitting these instructions tothe tool 30 and their execution by the tool.)

The system also monitors if the surgical tool performing the mixing hasbeen actuate for a time equal to the mix duration, step 862. Once instep 862 it is determined that the cement is mixed for the selectduration, surgical tool 30 is deactivated, step 864. This deactivationmay occurred based on the tool control processor (DSP 170) generating azero speed USER_SPEED signal automatically at the end of the mix timebased on the stored instructions. Alternatively, the remote unitgenerates a specific instruction to the surgical tool 30 instructing thecontrol processor to assert the zero speed USER_SPEED signal.

The current drawn by the tool motor 34 immediately prior to thedeactivation of the tool 30 is also again tested, step 866. In step 866,this current drawn is tested to determine if it is above the acceptablelevel expected at the end of the mixing process. The system interprets apositive determination as indicating the mixed cement has a viscosityhigher than expected. This means the mixed cement will be more difficultto work and have a shorting set time. Thus, if the determination of step866 is positive, the system, in step 868, presents a warning regardingthe exception state of the cement. If the surgical personnel elect touse the cement, they enter an acknowledgement into the system, step notshown.

If the evaluation of step 866 tests negative, then the cement has anacceptable viscosity. The system, as represented by step 870, generatesa message indicating that the cement mixture is satisfactory.

Once the cement mixing is complete, the system, in step 872 determinesthe expected set time. One input variable made to make thisdetermination is the last measure of current drawn by the motor 34. Asdiscussed above, these data are proportional to the final viscosity ofthe cement. The other input variable used to make this determination arepreviously entered data: cement type; ambient temperature; ambientrelative humidity; additives including quantity; and (if present) mixingunit heater temperature.

The determination of set time in step 872 is performed using methodologysimilar to that employed in step 836 to determine mix duration.Empirically derived reference data are used to generate the look-uptables, constants, coefficients and/or exponents used in step 872 todetermine set time. Table 2 lists general relationships between uncuredcement post-mix and set time.

TABLE 2 General Relationships Between Cement Post-Mix Input VariablesAnd Set Time Type of Cement, i.e., Shorter Set Time Increased CementViscosity High Motor Current Draw At End Of Mix Shorter Set TimeAddition of Additives Longer Set Time High Ambient Temperature ShorterSet Time High Ambient Rel. Humidity Shorter Set Time Mixing Unit HeaterShorter Set Time

Once the set time is determined, step 872 concludes with a display ofthis time. It should be understood that step 872 may be performed as asubstitute for or after the current draw test of 868. In these versionsof the invention, if it is determined that the set time is too short,for example only 80% or 90% of the surgeon selected set time, warningdisplay step 870 is then executed.

It should likewise be understood that, based on surgeon preference, instep 872 the system calculates and displays cement working time.

In a step 874 the system, (personal computer 544) clocks down thedisplay indicating the set time. The system also monitors when the timeapproaches the expected set time, step 876. As the set time approaches,in step 878 a warning is provided. This warning, in addition to beingvisual, may be the audible. It should also be understood that as thecement is mixed, the current drawn by the motor 34 continually remainsbelow the acceptable minimal level. If this event occurs, the mixingprocess will increase beyond a set time boundary. In step 882, (FIG.26E) the system monitors the time of mix duration to determine if it isexcessive. If this determination tests positive, a warning is presented.This provides the surgical personnel with notice that there may besomething abnormal in the components used to mix the cement.

The above configuration of the system of this invention automates themixing of surgical cement. Surgical personnel are automatically informedof mixture components that should be used to form the cement such ascement type and quantity, monomer type and quantity, desirable/requiredadditives as a function of the components, the implants, with which thecement is to be used. This reduces the likelihood that potentiallyimproper components or component quantities will be introduced into thecement mixture. Similarly, based on the components used to form thecement, the surgeon preferences and the mixing system components, thetime and process by which the components are mixed together isautomatically calculated. This reduces the time required to make thesecalculations and the likelihood human error could result in inaccuratecalculations.

During the actual mixing process, the system of this invention regulatesthe operation of the tool 30 employed to perform the mixing. Surgicalpersonnel are not required to devote appreciable mental or physicaleffort to ensure the tool properly mixes the components together formingthe cement. Again, owing to the automated control of the tool 30, thelikelihood human error will result in excess or insufficient mixing issubstantially reduced.

Once the mixing process is completed, the system provides an immediateindication of whether or not the cement may be to viscous or set tooquickly for use. The system also provides data indicating when thecement will set. Thus, if the surgeon indicated that he/she wanted thecement to have a set time of 10 minutes, the system indicates if the settime may be less, for example 9:30 minutes. This information lets thesurgeon know that it may be necessary to perform certain parts of thesurgical procedure at a relatively fast rate. Alternatively, if the datagenerated by the system indicates that the set time will be reached at aslightly longer time, for example 11:00 minutes instead of 10:00minutes, the surgeon is likewise made aware of this fact so that he/sheis aware of this fact and can adjust performance of the procedure as isappropriate.

VI. Auxiliary Unit Communication and Power Sharing

As discussed above, an auxiliary unit such as a transceiver head 530 ortracker 539 (both in FIG. 17), may be fitted to the powered surgicaltool 30 of this invention. Other types of auxiliary units that may be soconnected are laser pointers and light sources. Still another class ofauxiliary unit performs a sensing function. One such auxiliary unit isincludes an infra-red transducer. This type of auxiliary unit is used tomonitor the temperature of the tissue at the surgical site.

FIGS. 32 and 33 illustrate how a surgical tool 30 d of this invention isprovided with contacts 920 over which data signals are exchanged withthe auxiliary unit. Contacts 920 also serve as the conductive membersover which power from the tool battery 42 (FIG. 6E) is selectivelysupplied to the auxiliary unit.

Tool 30 d has a housing 32 d with a head 36 d from which handle 38 dextends. Housing 32 d is formed so as to have a head bottom surface 910of head 36 d that extends proximally from handle 38 d is planar. A cap912 closes the open proximal end of housing head 36 d. The base of cap912 is coplanar with head bottom surface 870. Two spaced apartrectangular indentations 914 are formed in the bottom flat surface ofcap 872. Tool 30 d is shown with a single switch 46.

Head bottom surface 910 is formed with a rectangular cut-out 916 thatopens to where the edge along which cap 912 abuts housing 32 d. Aterminal 918 is seated in cut-out 876. Contacts 920, which extenddownwardly towards handle 38 d, are part of terminal 918. In theillustrated version of the invention four contacts 820 are provided.

FIG. 34 illustrates the components internal to the tool 30 d to whichcontacts 920 are connected. Two contacts 920 are communicationscontacts. In one version of the invention, communication between thetool 30 d and the auxiliary unit is in accordance with the I²C protocolavailable from Philips Semiconductor. Accordingly, a first one of thecontacts 920 is the contact over which clock signal, SCL signals, aretransmitted. A second contact 920 is the contact over which serial datasignals, SDL signals, are exchanged. In FIG. 34 each contact 920 thatfunctions as a communications contact is connected to the DSP 170 a.More particularly, each contact is connected to the DSP 170 a through aresistor 886. A diode 888 is series connected across each resistor 886.Diodes 888 provide low resistance bypass paths around the resistors 886for the SCL and SDA signals emitted from the DSP 170 a to the auxiliaryunit.

A reverse bias zener diode 890 is connected between each I²C pin on DSP170 a and ground. Diodes 890 thus protect the DSP 170 a from voltagespikes.

A third one of the contacts 920 functions as the conductive member overwhich the charge in the tool battery 42 is supplied to the auxiliaryunit. Battery 42 is selectively tied to the contact 920 by a normallyopen p-channel FET 896. The BATT+ signal is applied to the drain of FET896. The contact 920 is tied to the FET source. The BATT+ is appliedthrough a resistor 898 to the gate of the FET 896 so as to normally holdthe FET open.

An n-channel FET 902 drives the voltage at the gate of FET 896 below thesource voltage so as to selectively switch FET 896 closed. The source ofFET 902 is connected to the gate of FET 896 by a resistor 904. The drainof FET 902 is tied to ground. FET 902 is gated by a single asserted fromDSP 170 a. A zener diode 906 is reverse bias connected between the BATT+pin and the junctions of resistors 898 and 904. A diode 908 is reversebias connected between the source of FET 896 and ground.

Normally, the BATT+ signal applied through resistor 898 to the gate ofFET 898 holds FET 898 in the off state.

An auxiliary unit (not illustrated) may have open faced shell thatallows the unit to be fitted over the proximal end of the housing head36 d. When the shell is so positioned, moveable fingers integral withthe shell seat in housing indentations 874. A latch mechanism, part ofthe auxiliary unit, holds the fingers in the indentations so the fingershold the auxiliary unit to tool 30 d.

Data from the auxiliary unit received over the I²C communications linkmay inform the DSP 170 a that the auxiliary unit is allowed to draw thepower stored in the battery 42. In the event the auxiliary unit is soauthorized, DSP 170 a asserts a signal to gate FET 902. FET 902 thuscloses so as to tie resistor 904 to ground. This results in the voltagepresent at the gate of FET 896 dropping below the voltage of the sourceso as to turn the FET 896 on.

As seen in FIG. 34, the fourth contact 920 establishes a connectionbetween the circuit internal to auxiliary unit and the ground of thecircuit of tool 30 d.

Sealed module 40 of the surgical tool 30 of this invention does morethan simply protect the circuit components that regulate actuation ofthe tool power generating unit (motor 34) and that monitor the useractuated control members (trigger switches 46 and 47). Module 40 alsoprotects the sensors (Hall sensors 74 and 76) that generate outputsignals representative of the operating state of the power generatingunit. Sensors 74 and 76 are not exposed to the harsh moist environmentof autoclave sterilization. By so protecting the sensors, the likelihoodof their failure is reduced.

Still another feature of versions of the surgical tool 30 of thisinvention that include motor 34 is that only two sensors, Hall sensors74 and 76, are required to provide signals representative of theposition of motor rotor 78. This reduces by one the number of sensorsnormally employed to provide the feedback needed to monitor the positionof a brushless DC motor. This represents a cost savings overconventional monitoring assemblies.

Also, the use of the two Hall sensors 74 and 76 and the means by whichthey provide an accurate means to determine rotor position when themotor is at start up, the 0 RPM state, eliminates the need to employother means that may consume significant amounts of power to start themotor and determine initial rotor position. This is especially useful inversions of this invention wherein the power to energize the motor isfrom battery 42. The minimization of reduced power draw at startup ofthis invention serves to increase the overall time any one battery canbe used to power the motor 34 before the battery is discharged.

The construction of the power control module 40 has other advantages. Inparticular, mounting plate 119 serves more functions as just the memberto which FETs 82 a-82 c, 84 a-84 c and 336 a-336 c are mounted. Mountingplate 119 serves as a heat sink for drawing heat away from the FETs tothe tool housing 32. Mounting plate distal end section 121 functions asa spacer to prevent the module front plate 92 from abutting the proximalends of the trigger switches 46 or 47. Such contact, if allowed tooccur, can adversely affect the pattern of the magnetic fields emittedby magnets 56 and 57.

During assembly of the control module 40, mounting plate functions as abacking for circuit board 64. This eliminates the need to introduce aseparate backing plate into the assembly process in order to performwire bonding between FETs 84 a-84 c and 336 a-336 c and the adjacentsurface of the circuit board. Once control module 40 is manufactured,mounting plate 64 functions as a support bracket for the circuit board64.

Still another feature of surgical tool 30 of this invention is that,unless the tool is being actuated or was just actuated, the controlcircuit components are in the sleep mode. When the control circuitcomponents are in this mode, less power is consumed than when they arein the active mode. This arrangement minimizes the draw on battery 42.When either trigger switch 46 or 47 is initially displaced from theat-rest position, sensor 66 or 70 essentially immediately undergoes astate change. This results in the rest of the control circuitessentially simultaneously transitioning into the awake mode. Thus,while this feature of the invention serves to reduce current draw on thebattery 42, it does not noticeably affect operation of the tool.

Surgical tool 30 of this invention is further constructed so thatcontrol processor internal to the tool (DSP 170) is selectivelyprogrammed to vary the tool control signals generated as a function ofthe depression of the actuating members (trigger switches 46 and 47). Asindicated by the above described processes, this feature of theinvention makes it possible for the operation of the tool powergenerating unit (motor 34) based on the actuation of the member to becustom set based on doctor preference, type of attached surgicalattachment 41, procedure being performed or point in the procedure.Thus, a cordless surgical tool 30 of this invention can be customconfigured and custom operated in essentially the same ways that,previously, only corded tools could be so configured and operated.

VII. Alternative Embodiments

The above descriptions are directed to specific embodiments of thisinvention. Other versions of the invention may have features differentfrom what has been described. For example, while the described motor hasa rotating shaft, other motorized surgical tools of this invention havedrive members that oscillate or reciprocate.

It should likewise clear that this invention is not limited to surgicaltools with motors. Other surgical tools of this invention may have otherpower generating units such as units designed to emit RF energy, heat,light energy or ultrasonic energy.

The type of sensing transducer internal to the control module thatmonitors the operation of the power generating unit is a function of thetype of power generating unit. For example, if the power generating unitemits RF energy, internal to the unit may be an inductor that generatesa magnetic field as a function of the power emitted by the unit.Internal to the module is a sensor similar to the described Hall effectsensors that monitor the strength of the magnetic field. Alternatively,the power generating unit may emit light, in the ultra-violet, visibleor infrared spectrum as a function of the operating state of the unit.For example a fraction of the light emitted by a light-generating powergenerating unit may be diverted towards the control module.Alternatively an RF power generating unit may include a member thatemits an infra-red light signal as a function of the extent to which thesurgical site to which the associated surgical attachment is heated. Inthese versions of the invention, the structural component of the moduleincludes a window that is transparent to the type of light emitted bythe power generating unit or the surgical site. Internal to the controlmodule, behind the window, is a transducer sensitive to the spectrum ofemitted light.

Alternatively, the transducer assembly internal to the control module issensitive to mechanical energy emitted by the power generating unit. Forexample, if the power generating unit includes a vibrating transducer,the surgical tool may have a conduit through which a fraction of thegenerated vibrations are transmitted to the control module. In thisversion of the invention, the structural wall of the control module isformed from material that does not appreciably attenuate thesevibrations. A motion-sensitive transducer internal to the control modulegenerates signals in response to the output vibrations.

It should similarly be appreciated that, even in versions of theinvention wherein the power generating unit is some type of motorassembly, the sensor assembly internal to the control module thatremotely monitors the operation of the power generating unit need notalways be magnetic strength sensor. For example, in some versions of theinvention, the control module sensor is photo-sensitive unit responsiveto light emitted or reflected by the motor. In these versions of theinvention, motor 34 is provided has a moving surface along whichmaterial of different reflectivity is applied. A light is emittedtowards the moving surface. Internal to the control module is aphotosensitive transducer that monitors the light reflected from a fixedarea. As the moving surface transits across the fixed area, the amountof reflected light detected by the sensor varies with the reflective ofthe applied material. Thus, in this version of the invention, a sensordisposed in the control module provide feedback regarding the operatingstate of a mechanical power generating unit without monitoring magneticfields. An inductor that may or may not be magnetically biased may alsofunction as the sensor.

Similarly, in some versions of the invention, the sensor internal to thecontrol module is sensitive to mechanical motion, vibrations emitted bythe motor and transmitted through the control module.

Further in some versions of the invention, a flux pipe may serve as aconduit for transmitting energy emitted by the tool power generatingunit to the control module. Diagrammatically, such an assembly isillustrated by FIG. 35. Here a flux pipe 924 that serves as a goodconductor for the emitted energy or is transparent to the energy extendsfrom the power generating unit 34. For example, if the magnetic energyis emitted by the power generating unit 34, flux pipe 924 is formedmaterial with high magnetic permeability. (In this situation, the fluxpipe may actually include a center core of highly magnetically permeablematerial, an inner sleeve of relatively impermeable material and anouter sleeve of highly permeable material.) If the emitted energy islight energy, flux pipe 920 is formed from material relativelytransparent to the light emitted by the power generating unit. The freeend of the flux pipe terminates adjacent the control module structuralmember enclosing the module sensor. An advantage of this construction ofthe invention is that it makes it possible to position the controlmodule at a distance from the power generating unit further away than itmay otherwise be possible to locate module.

Similarly, it should be recognized that there is no requirement that inall versions of the invention, control module 40 be hermetically sealed.Manufacturing economics or other factors may make it undesirable to soassemble the control module. Thus, in some versions of the inventionwhere it is still necessary to protect the components internal to themodule from the rigors of sterilization, the module may be filled with apotting compound.

Likewise, there is no requirement that all versions of the inventionhave each of the above-described components. Thus, in some versions ofthe invention, the control module may not include sensors for monitoringthe actuation of the manually actuated control members. Similarly, thereis no requirement that tool 30 of this invention always be cordless.Similarly, while in many versions of this invention, Hall sensor 74 and76 that generate signals representative of the position of the motorrotor be mounted in the control module, that need not always be thecase. In some versions of this invention, for example tools of thisinvention wherein the sensors do not have to be protected from a harshenvironment, manufacturing economics or other factors may require thatone or both of the sensors 74 and 76 be placed outside the controlmodule. For example, these sensors may be placed in the tool relativelyclose to the motor rotor 78.

Also, there may be some tools wherein it is desirable to provide thecontrol assembly with the power FETs on mounting plate arrangement ofthis invention. However, for other reasons, neither the actuating membersensors nor the power generating unit sensors are disposed in themodule. In these versions of the invention the control assembly may noteven be a sealed module.

It should similarly be appreciated that that the inventive features ofthis tool may be employed in tools other than surgical tools.

In motorized tools constructed in accordance with this invention whereina Hall sensor 74 is employed to generate signals representative of theposition of the motor rotor 78, there may not be any need to perform theprocess described that continually update the signal reference levelsfor determining when the HALLx signals undergo state transitions. Thisupdating may be eliminated if empirical analysis determines that theoutput signal from Hall sensor 74 remains relatively steady over time oftool operation and with changes in temperature. Eliminating these stepsreduces the process steps needed to be performed by the controlprocessor (DSP 170).

Also, the process steps practiced by the system and method of thisinvention may differ from what has been described. For example, in step494, the control processor (DSP 170) uses Equation 1, a linear equation,based on trigger displacement, generate the USER_SPEED signal. Equation1 is an example of just one equation that can be used to generate theUSER_SPEED signal. Alternatively the control processor can be set togenerate a USER_SPEED signal that varies non-linearly as a function oftrigger displacement.

For example, plot 930 of FIG. 36 illustrates how, if Equation 1 ismodified, control processor (DSP 170) outputs a USER_SPEED signal thatincreases exponentially with the displacement of the trigger switch,Plot 930, while being generally exponential also has a discontinuity932. Discontinuity 932 represents how it control processor 170 canfurther be programmed to generates USER_SPEED signals that skip overcertain speeds. One reason this discontinuity may be desirable is toprevent the rotation of a surgical accessory 41 such as a bur at a speedequal to the natural resonant frequency of the bur. By avoiding thedriving of the bur at the frequency, the extent to which the burvibrates while being actuated is minimized.

Similarly, the processes employed to operate the tool of this inventionmay vary owing to the use of different components. For example, thetests of step 378 to determine rotor position at start-up, 0 RPM, arebased on the assumption that sensor 76 is electrically within 60° ofsensor 74. In an alternative construction of the invention, sensor 76 iselectrically between 60 and 120° of sensor 74. In these versions of theinvention, sensor 76 may even output a digital signal as a function ofrotor position. In FIG. 9, this signal is represented by plot 908.

Here, at start up, in step 378, the determination of the particular(electrical) sextant in which the rotor is located is made according tothe following process. If the normalized output signal from sensor 74indicates the rotor 78 is in either that 0 to 60° sextant or the 120 to180° sextant, a test is made to determine if:

sensor 76 signal>0

If this determination tests false, then collectively the sensor signalsindicate the rotor is in an angular position between 0 and 60°. If thisdetermination tests true, collectively the signals indicate the rotor isin a position between 120 and 180°. If the normalized output signal fromsensor 74 indicates the rotor is in either the 180 to 240° sextant orthe 300 to 360°, the above test of the output signal from sensor 76 isexecuted. Here, if this determination tests true, then the sensorsignals indicate the rotor is in an angular position between 180 and240°. If this determination tests false, then the rotor is in a positionbetween 300 and 360°.

An advantage of the above version of the invention is that it eliminatesthe need to precisely set the amplitude of the output signals forsensors 74 and 76 relative to each other. In the previously describedversion of the invention, such regulation is required in order togenerate the signals on which the described comparisons can beperformed. (The degree of signal regulation is inversely related to theelectrical phase difference of the sensors 74 and 76 from each other.)Since, in this version of the invention, the signal from sensor 76 iscompared to a reference value, no such regulation is required. Also, inthis version of the invention, the sensor 76 can be either output ananalog or digital signal.

It may even possible to determine the position of the motor rotor atstart up, in which portion of the signal cycle the signal is in, withoutthe signal from the supplemental sensor, sensor 76. FIG. 37 illustratesthe process steps executed using a base assumption algorithm to performthis process. In this process, in step 940, based on the signal fromsensor 74, the DSP determines outputs an initial signal, SNS_(INIT).This means that rotor position is either in the first sextant thatincludes point 942 or the third sextant that includes point 962 of FIG.38. For purposes of simplification, FIG. 38 is a plot of the signal outof sensor 74 for a two-pole rotor. Thus the single 0 to 360° signaloutput by motor rotor sensor 74 corresponds to a single rotation ofmotor rotor 78. In a step 946, DSP asserts start-up signals to the motorbased on the assumption that the SNS_(INIT) signal from sensor 74indicates that the rotor 78 is in the first sextant. As represented bystep 948, the DSP 170 continues to monitor the signal from sensor 74.

If the assumption upon which the execution of step 946 is based iscorrect, and the rotor will turn in the selected direction. This resultsin the SNS signal output by sensor 74 undergoing an appreciable changefrom the SNS_(INIT) level. In other words, the ΔSNS/Δtime slope isappreciable. In FIG. 37, this is represented by the level of theSNS_(T1) ^(ASMPTN_CRCT) signal, represented by point 949, beingappreciably different from the level of the SNS_(INIT) signal. Thus, ina step 950, based on the next measured signal, the SNS_(T1) signal fromsensor 74, the DSP determines the magnitude of the ΔSNS/Δtime slope. Ina step 952 the magnitude of the ΔSNS/Δtime slope is compared to a targetslope. If the magnitude of the calculated slope is at least as great asthe target slope, DSP 170 interprets this result as indicating theinitial assumption was correct; the rotor was in the first sextant ofrotation. The DSP 170 therefore continues to assert control signal basedon the initial assumption, now proven correct, regarding rotorrotational position, step 954.

However, the SNS_(INIT) signal may actually be indicating that the rotorat start-up was in the third sextant, the sextant associated with thesignal at point 962. In this situation, the energization signals appliedto the motor coils based on the incorrect assumption of rotor positionof step 946 will not cause the rotor to appreciably move. Instead, atleast for a short time, the signals applied to the motor coils will onlycause a small movement of the rotor until the rotor enters a lockedposition. Given this relatively small angular displacement of the motorrotor, the level of the SNS_(T1) ^(ASMPTN_INCRCT) signal output from thesensor 74 will likewise only be marginally different from the SNS_(INIT)signal level. In FIG. 37 this is represented by the relatively smalldifference between the signal levels at points 962 and 965.

Thus, in this situation, in step 950, when the ΔSNS/Δtime slope iscalculated, the slope will relatively small. In the test of step 952 thecalculated slope will be less than the target slope. The DSP 170interprets this result as indicating that, in fact the rotor was not inthe first sextant of rotation but actually in the third sextant.Therefore, in a subsequent processing step, step 966, the DSP continuesto assert control signals to the MCC 172 based on the revised and provencorrect interpretation of rotor position.

It should be understood that in the above process step, the test of step952 is based on the absolute slope. The positive or negative gradient ofthe slope is irrelevant as this is a function of the direction of rotormovement.

Alternative means may be employed to avoid the need to provide twosensors for determining rotor position at start up. In anotheralternative scheme, the control circuit, at start up, first appliescurrents to the coils that cause the motor rotor to turn to a knownposition that can be determined from the peak or valley signal from thesingle sensor 74. Once sensor 74 indicates the rotor is in this state,additional start up signals are applied to rotate the rotor from theknown state.

It should likewise be understood that communications protocols otherthan I²C may be used to exchange signals with the tool control processor(DSP 170). One alternative protocol may be the one-wire protocoldeveloped by Dallas Semiconductor.

In alternative versions of the invention, DSP 170 can perform some ofthe control functions performed by the motor control circuit 172. Forexample, the DSP 170 can regulate operation of the tool 30 when the toolis to be driven in the oscillate mode. In this version of the invention,the DSP monitors the degrees of rotation the motor rotor 78 turns ineach direction of an oscillate cycle. At any given instant the DSP onlyasserts a single one of the FORWARD or REVERSE signals to the MCC. Oncethe DSP determines the rotor has turned a set number of degrees in onedirection, for example the “reverse” direction, it switches fromasserting the REVERSE signal to the FORWARD signal. This switch ofinstruction signals causes the MCC to stop asserting signal that causethe rotor to turn in the reverse direction and start asserting signalsthat cause the rotor to turn in the forward direction.

An advantage of the above arrangement is that surgeon can program theDSP 170 so that the DSP causes the motor rotor to oscillate in anunequal rotational sequence. For example, by using the DSP to regulateoscillate, tool 30 can be configured so that the rotor, moreparticularly after speed reduction, the attachment rotates first 720° ina first direction and then 360° in the second direction before repeatingthe sequence. Other sequences are also possible, for example 720° in thefirst direction, 360 in the second direction, 360° in the firstdirection and 360° in the second direction before repeating are alsopossible.

Further, by allowing the DSP to regulate oscillation, the DSP can rampup and ramp down the rotor speed at, respectively the start-up and endperiods of the rotation in each directional cycle. This dampening of theacceleration and deceleration (braking) of the rotor can reduce toolvibration.

Also, it should be understood that the control functions of the systemof this invention may further vary from what is described. Clearly, asurgeon can reconfigure control function of each trigger switch 46 and47 during the middle of the procedure. Also, when plural tools 30 areused one may be used as an override of the other. Thus, in a teaching asituation the instructor's tool 30 a is configured so that when onetrigger switch is depressed, the control processor generates a stopcommand for execution by the second tool 30 b. This stop command istransmitted through the tool data transceiver head 530 to the wirelesstransceiver head 536. After receipt by the wireless transceiver head536, head 536 or another component causes the stop command to betransmitted to the student's handpiece 30 b. In this configuration ofthe system the second trigger switch of the instructor's handpiece 30 ais configured to actuate the power consuming unit internal to thathandpiece to allow the instructor to complete the procedure.

Also, the manually set actuator(s) used to regulate operation of thesurgical tool 30 may vary from the disclosed trigger switches. In someversions of the invention, the tool may only have a single triggerswitch. In these versions of the invention, the tool may have a bi-statelever arm. The surgeon selectively sets the lever arm based on theoperating mode in which he/she wants to operate the tool. Thus if thepower generating unit internal to the tool is a motor 34, some of thebistate settings that can be regulated by the setting of the lever armare: forward/reverse; forward/oscillate; and low speed/high speed. Withthese versions of the invention, in steps 360 and 262, the bistateoperational ranges for the tool are loaded into the control processor(DSP 170).

Likewise, in versions of the invention wherein motor 34 functions as thepower generating unit, during start-up the two sensors may be used todetermine rotor position as described. Then, post start up, two or moresensors are used to determine the subsequent positions of the spinningmotor rotor.

Similarly in other versions of the invention, the manual actuators maynot be trigger switches. In these versions of the invention, one or morepush buttons mounted to the tool housing 32 regulate the actuation ofthe power generating unit. Each push button may, for a short period oftime, bring a magnet in sufficient proximity to an associated controlmodule sensor that the output signal from the sensor undergoes a statetransition. These types of control members are appropriate forregulating the actuating of power generating units that are suited tostep level control. RF ablation tools are one such type of tool.

In some versions of the invention, the sensor or sensors used todetermine if a switch has been actuated, sensors 66 and 70 in thedescribed embodiment, may not be digital sensors. In alternativeversions of the invention, the sensors may be analog sensors. Thesesensors may even be microswitches or reed switches. In these versions ofthe invention, the wiper integral with the switch makes or breaks aconnection based on displacement of the associated switch.

Alternatively, it may be possible to eliminate sensors 66 and 70 fromsome versions of the invention. The signal from a sensor used to monitorswitch actuation is employed by a first circuit to control the actuationand negation of the AWAKE signal. The signal is then used by a secondcircuit to produce an output signal representative of the user desiredoperating rate for the power generating unit internal to the handpiece.

It should likewise be recognized that while, in many versions of theinvention, coupling assembly 39 allows the surgical attachment 41 to beremovably attached to the tool 30, that is not always the case. In someversions of the invention, coupling assembly 39 is a fastening device orfastening assembly that permanently holds the surgical attachment tohousing 32 and the power generating unit. These assemblies are common indisposable versions of this invention.

It should thus be appreciated that the other individual components fromwhich the tool of this invention are formed may vary from what has beendescribed. A conventional microprocessor may function as the toolcontrol processor. Plural components may substitute for the ASIC formingthe motor control circuit 172. In some versions of the invention, thesignals asserted by sensor 66 or 70 when magnet 56 or 58, respectively,is first asserted may function as the AWAKE signal. This eliminates theprocessing required by the DSP 170 otherwise required to assert thissignal.

Internal to the handpiece housing 32 there may be a nonvolatile memoryto which data are written to by the control processor (DSP 170). Thismemory functions as the tool log in which the data regarding the tooloperation, including the particulars regarding the when and what ofexceptional events occurred.

Similarly, the processes of this invention may be executed using lesssteps or in alternative arrangements of the steps than what has beendescribed.

Therefore, it is the object of the appended claims to cover all suchvariations and modifications as come within the true spirit and scope ofthis invention.

What is claimed is:
 1. A surgical system comprising: a surgical toolcomprising: a housing; a variable speed motor disposed in said housing;a tool control module disposed in said housing, said control modulehaving a control circuit selectively actuating said motor; a surgicalnavigation system configured to track the position of said surgical toolrelative to a user defined zone, said surgical navigation systemcomprising: a navigation console in communication with said tool controlmodule; and wherein upon said navigation system determining saidposition of said surgical tool has entered said user defined zone, saidnavigation console is configured to communicate a first instruction tosaid tool control module to deactivate said motor; and wherein upon saidnavigation system determining said position of said surgical tool hasentered said user defined zone, said navigation console is furtherconfigured to provide an override option that is selectable by a user ofsaid system, and upon selection of said override option by said user,said navigation console is configured to communicate a secondinstruction to said tool control module to continue operation of saidmotor.
 2. The surgical system of claim 1, further comprising a triggerswitch manipulatable between a first position and a second position forcontrolling actuation of said variable speed motor; a trigger sensor incommunication with said tool control module and configured to detect theposition of said trigger switch and to communicate a second signal tosaid tool control module indicative of said position of said triggerswitch.
 3. The surgical system of claim 1, further comprising a firstattachment that is removably couplable to said surgical tool; whereinsaid first attachment comprises a first identification componentincluding data specific to characteristics of said first attachment; andwherein said surgical tool comprises a reader in communication with saidtool control module and configured to read said data from said firstidentification component when coupled to said surgical tool; whereinsaid tool control module is configured to update operationalcharacteristics of said surgical tool based, at least in part, on saiddata read from said first identification component of said firstattachment.
 4. The surgical system of claim 1, wherein said surgicalnavigation unit is configured to inhibit actuation of said tool byinhibiting actuation of the motor.
 5. The surgical system of claim 1,wherein said surgical navigation unit is further configured to, based onthe position of said surgical tool, regulate the speed of said motor. 6.The surgical system of claim 1, wherein said system further comprises afirst attachment and a second attachment, each of said first attachmentand said second attachments removably couplable to said surgical tool;wherein said first attachment comprises a first identification componentincluding data specific to characteristics of said first attachment;wherein said second attachment comprises a second identificationcomponent including data specific to characteristics of said secondattachment; and wherein said surgical tool comprises a reader incommunication with said tool control module, said reader configured toread said first identification component or said second identificationcomponent of said first attachment or said second attachment that iscoupled to said surgical tool; and wherein said tool control module isconfigured to update operational characteristics of said surgical toolbased, at least in part, on which of said first attachment or saidsecond attachment is coupled to said surgical tool.
 7. The surgicalsystem of claim 1, wherein said navigation console is programmable bythe user to define said user defined zone.
 8. The surgical system ofclaim 1, wherein said navigation console is programmable by the user todefine operational characteristics of surgical tool based, at least inpart, on the position of said surgical tool relative to said userdefined zone.
 9. A method of operating a surgical tool having a variablespeed motor using a navigation system to track the position of thesurgical tool while performing a medical procedure on a patient, saidmethod comprising: receiving patient data representative of thepatient's anatomy that is uploaded to the navigation system; defining azone within the patient data stored on the navigation system; using thenavigation system, determining the position of the surgical instrumentrelative to the defined zone; wherein upon the navigation systemdetermining the surgical instrument has entered the defined zone:deactivating the variable speed motor of the surgical instrument;presenting a user selectable override option; and upon the userselecting the override option, continuing operation of the variablespeed motor of the surgical instrument while within the defined zone.10. The method of claim 9, wherein the step of continuing operation ofthe variable speed motor of the surgical instrument while within thedefined zone further comprises the navigation system signaling thesurgical tool to operate the variable speed motor at a speed less than amaximum operating speed of the variable speed motor.
 11. The method ofclaim 9, further comprising providing a visual warning to a user uponthe surgical tool crossing the defined zone.
 12. The method of claim 9,further comprising coupling a surgical attachment to the surgical tool,wherein the surgical attachment comprises an identification componentincluding data specific to a characteristic of the surgical attachmentthat can be read by a reader on the surgical tool.
 13. The method ofclaim 12, further comprising operating the surgical tool based, at leastin part, on data read from the identification component of the surgicalattachment coupled to the surgical tool.
 14. The method of claim 12,further comprising removing the surgical attachment from the surgicaltool; coupling a second surgical attachment to the surgical tool,wherein the second surgical attachment comprises a second identificationcomponent including data specific to a characteristic of the secondsurgical attachment that can be read by the reader on the surgical tool.15. The method of claim 14, further comprising operating the variablespeed motor of the surgical tool based, at least in part, on data readfrom the second identification component of the second surgicalattachment coupled to the surgical tool.
 16. A surgical systemcomprising: a surgical tool comprising: a surgical handpiece including avariable speed motor; a handpiece control console in communication withsaid surgical handpiece, said handpiece control console configured toselectively energize said surgical handpiece; a footswitch incommunication with said handpiece control console for controllingoperation of said surgical handpiece; a surgical navigation systemconfigured to track the position of said surgical handpiece relative toa user defined zone, said surgical navigation system comprising: anavigation console in communication with said surgical tool; and whereinupon said navigation system determining said position of said surgicalhandpiece has entered said user defined zone, said navigation console isconfigured to communicate a first instruction to said surgical tool todeactivate said surgical handpiece; and wherein upon said navigationsystem determining said position of said surgical tool has entered saiduser defined zone, said navigation system is further configured toprovide an override option that is selectable by a user of said surgicalsystem, and upon selection of said override option by said user, saidnavigation console is configured to communicate a second instructionsaid surgical tool to continue operation of said surgical handpiece. 17.The surgical system of claim 16, wherein selection of said overrideoption configured to continue operation of said surgical handpiece at anoperating rate less than a maximum operating rate when said surgicalhandpiece is within said user defined zone.
 18. The surgical system ofclaim 16, further comprising a first attachment that is removablycouplable to said surgical handpiece; wherein said first attachmentcomprises a first identification component including data specific tocharacteristics of said first attachment; and wherein said surgicalhandpiece comprises a reader configured to read said data from saidfirst identification component when coupled to said surgical tool; andwherein said handpiece control console is configured to updateoperational characteristics of said surgical tool based, at least inpart, on said data read from said first identification component of saidfirst attachment.
 19. The surgical system of claim 16, wherein saidsystem further comprises a first attachment and a second attachment,each of said first attachment and said second attachments removablycouplable to said surgical handpiece; wherein said first attachmentcomprises a first identification component including data specific tocharacteristics of said first attachment; wherein said second attachmentcomprises a second identification component including data specific tocharacteristics of said second attachment; and wherein said surgicaltool comprises a reader configured to read said first identificationcomponent or said second identification component of said firstattachment or said second attachment that is coupled to said surgicaltool; and wherein said handpiece control console is configured tooperate said surgical handpiece based, at least in part, on which ofsaid first attachment or said second attachment is coupled to saidsurgical handpiece.
 20. The surgical system of claim 16, wherein saidnavigation console is programmable by the user to define operationalcharacteristics of surgical tool based, at least in part, on theposition of said surgical handpiece relative to said user defined zone.